The last time Sandrine Jourdan was seen she was walking up a friend's driveway in the Sunshine Coast.

That was on July 13.

Since then she has not accessed her bank accounts, used her phone or wished two of her children a happy birthday.

Her family have launched a desperate search for her, creating a Facebook page, making a YouTube video and her sister, Christine Jourdan, spent $2000 in one month calling every person she could find with a connection to her sister.

So why have you heard about Allison Baden-Clay and Jill Meagher, but this may be the first time you are reading the name Sandrine Jourdan?

Where is this missing woman's saturation media coverage? Why is her Facebook page not garnering tens of thousands of supporters?

Her family has campaigned relentlessly for the 90 days that Sandrine has been missing and her sister is at a loss as to why they have managed a handful of news articles in period when Mrs Baden-Clay and Ms Meagher dominated the headlines of all news outlets.

She is desperate to get her missing sister's story on television news and has called every station she could think of but described one television station in particular as "very rude".

"They turned around to us and said 'well what's so special about her? Please explain what's so special and maybe we'll do a story about her' and when we told them what was going on they said 'no, that's not newsworthy'," Ms Jourdan said.

"When they told us that we said 'you've got to be kidding me' ... two weeks later they ran a story about a dog being reunited in America and I was like 'that's where it could have been put in, just a photo of my sister'.

"I'm not asking you to do a full story, just put up a photo: 'Missing. Hey'."

Sandrine had broken up with her partner the month before she went missing and was staying with friends and family but had secured a new place to live before she disappeared.

Some friends said she had been planning to go on a Buddhist retreat so her siblings rang every Buddhist retreat in Australia but none had heard of Sandrine.

"For Sandrine just to go and not tell somebody where she is going is weird and the circumstances to it are just weird too because she was supposed to go with a friend to Motocross and she walked to the end of his driveway and by the time he drove to the end of his driveway she was no longer there," she said.

"...That was the last anybody heard or saw of her, since then I got hold of her phone bills and contacted every single person on her phone bills and in her phone book."

Ms Jourdan said she knew something was wrong straight away when her brother reported their sister missing.

But other people had tried to reassure her, saying perhaps her sister had "gone off to clear her head".

Then September 3, the 17th birthday of one of her daughters, came and went and she did not get a 'happy birthday' from her mother.

More people became more worried.

Then September 19 came and went and Sandrine's son turned 14 without a phone call, or even a Facebook post, from his mother.

Now everybody connected to her is sick with worry but the family still cannot get the word out.

When asked how the children are coping with their mother's disappearance, the answer is surprising.

"They are really upset that we can't get on to televisions to actually get it out there," Ms Jourdan said.

"... People are only just beginning to realise she is missing because the families have been pushing it so hard on Facebook and in newspapers which are our only outlets."

She has "absolutely no idea" why the disappearance of her beloved sister has barely raised the eyebrow of a journalist, yet media packs swarmed on the families and homes of Mrs Baden-Clay and Ms Meagher.

Well, there are a number of factors at play, according to journalism ethics expert from the Queensland University of Technology Leo Bowman.

And what it boils down to is the initial reaction to the disappearance from the police, the media and the general public.

If the police treat it as a potential homicide investigation from the outset then the media will follow and treat it seriously.

It also helps if there are attractive photos and a narrative is built around the missing person, which the public can relate to.

The most important and obvious factor is, the public have to care.

"If you don't get the first flush of publicity around it quite often it goes on the backburner because it is no longer considered a news story and there is no immediate thing," Dr Bowman said.

"People sometimes think when you've got a crime, they're not sure whether that person is in some way responsible or if they are a victim then maybe they put themselves at some risk themselves.

"There is this notion there are some people who are harmless and particular victims."

He cited Mrs Baden-Clay as an example of a relatable narrative, saying when she went missing the public very quickly knew she studied five languages and ballet and was a "wonderful mother".

"In her case and in the case of Jill Meagher we had very attractive photographs of the person and they look from the photograph to be a very nice person," he said.

"And that came up straight away, so people sort of identify with the narrative of the harmless victim.

"And they identify with qualities portrayed as someone they would like to know."

Dr Bowman said a difficulty in the Sandrine Jourdan case was there was no exact location where she went missing.

In the case of Daniel Morcombe and Mrs Meagher, people knew the exact site where they were last seen – a bus stop on the Sunshine Coast and walking home from a bar in Brunswick in Melbourne respectively.

He said the locations struck a chord with the public, allowing them to relate to the missing person on another level.

"A young kid ought to be able to catch a bus without getting killed and the sense with Jill Meagher is a young woman should be able to walk 500 or 600 metres to her home without [allegedly] getting abducted, raped and murdered," he said.

"We have that situation set up for us and then people say 'that could have been me, I walk along that road, my kids have often caught the bus'.

"She is someone just like me."

Mr Bowman said media usually gauged the newsworthiness of a missing person case from the initial reaction of the police.

If they seemed "a little bit nonplussed and puzzled" and did not come out strongly immediately, then the media would not come out strongly.

In the cases of Ms Meagher, Mrs Baden-Clay and Daniel, the outlook was "grim" fairly early. But in the case of Sandrine, there still seemed to be hope she would be found alive and ok.

"We do know, and police know, that people go missing all of the time but they don't always suspect, at least immediately, foul play," he said.

"So it is a little bit the way police play it, a little bit the way the media play it and what they have available to play with.

"It's [the coverage] a little bit to do with the way people come to view that person as 'someone I would like, identify with or someone I could admire'."

In late August, police renewed appeals for public help to find Sandrine.

The plea came after a thorough search of bushland, in the Caboolture area, was conducted by police and State Emergency Services volunteers but they failed to find her.

Ms Jourdan is known to frequent camping grounds in the Caboolture, Kilcoy, Moreton Island, Kenilworth and Sunshine Coast areas, north of Brisbane.

She is described as Caucasian in appearance, 164cm tall with a proportionate build with brown hair and brown eyes.

At the time of her disappearance, she was wearing a light mauve long sleeve jumper and dark dress pants.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or crimestoppers.com.au.