Rhianna Barreau disappeared from her Adelaide home in 1992. Police think the answers are close by.

On the morning of October 7, 1992, Rhianna Barreau was singing along to her favourite tune 'Loveshack' by the B-52s, and planning a wander down to the local newsagent to pick up a postcard. 

But what started as a completely ordinary Wednesday morning in the South Australian school holidays, turned into every parent's worst nightmare when 12-year-old Rhianna disappeared from her quiet suburban street. 

It's a case that continues to haunt those who grew up alongside it. A story without closure that remains attached to a $1million reward for answers. 

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A planned lunch meet up with her mum at the nearby TAFE had been abandoned that morning due to a bus strike affecting her commute. But we know that Rhianna instead made the one kilometre stroll from her Morphett Vale home to the Reynella Shopping Centre at about 10:30am, to pick up the postcard she planned to send over to her American pen pal. 

We know she headed home at about 12:30pm. 

We know she made it back inside; the postcard was found on the dining room table. 

But we don't know what happened next. 

Her mum arrived home around 4pm to find records strewn across the floor, the TV on and the front door locked. Her daughter was nowhere to be found. 

Was she coerced outside?

Did she head out to run another errand, and was intercepted by someone? 

Did she have plans with someone her loved ones didn't know about?

Why was the TV left on... did she leave in a hurry?

They're all questions that to this day remain unanswered, despite years of police inquiry.

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There was a widespread, early investigation launched in 1992 - police canvassed the streets from that evening, they erected mannequins in the local shopping centre wearing Rhianna's exact outfit. They organised re-enactments with one of her friends to share with the nightly news. 

But despite 1600 tips offs, none of the leads led them anywhere significant. 

As ABC reporter Rebecca Brice told Mamamia's True Crime Conversations, Rhianna's story is one that has lived in the back of her head for decades. So much so, she decided to dig back into the case in recent years to see if anything was missed.

Former homicide detective Allen Arthur told her, "From the time I went through the preliminary statements gathered by the two detectives from Major Crime and read all the additional information that was being gathered, I knew something was wrong, I knew she was in trouble."

28 years on, he reaffirmed that she "disappeared without a trace".

There were two key clues - a suspicious car that was reported. Firstly, a white LH Torana sedan with Victorian number plates. But police never found it.

Secondly, a set of keys believed to belong to Rhianna were also found on a nearby street. But the person who called that tip in from a local pay phone didn't end up producing them. 

"I would really like to have a policeman knock on our door tomorrow morning and say that here’s your little girl back in one piece, but the reality of that is fairly insignificant," Rhianna's father Leon told ABC TV News at the time.

The lack of evidence forced Arthur to abandon the more urgent police effort just a few weeks after her disappearance.

Posters were erected around town after Rhianna's disappearance. Image: Missing Persons Register.

Mannequins were put up in local shops to spark people's memories. Image: 7News.

Rhianna's friend did re-enactments of the day she went missing for police and media. Image: 7News.

As Brice explained, her recent chats with Arthur came with a sinister assumption. 

"In the words of Allen Arthur, 'somebody knows something, and we just need them to come forward'. I very much believe that with this case... If you talk to him about how things played out, he feels that someone got very, very lucky," she said. 

"My theory today is her abductor, and I will say killer, lives a lot closer than a lot of people think. And I would suspect that her remains are closer to where she lived than most people think," he told her.

Since writing her stories, Brice says a number of people have come forward to her with their thoughts and tips - some of which she has looked in too. 

"There are some interesting things that have come up about people in the area, about clues that do kind of match up, but never anything solid enough to go public with," she told True Crime Conversations.

Rhianna's case is part of an ongoing South Australian Police Operation, Persist, looking into cold cases. They've recently had some wins on very old cases in the state, including arrests in other decades-old murder and manslaughter cases.

"I think he's right," said Brice of Arthur's prediction. "I think it comes down to somebody who knows something coming forward with new information. 

"It's so hard to believe that a 12-year-old girl can go missing in broad daylight and never be seen again..."

If you know something about what happened to Rhianna Barreau, you can submit an anonymous tip here, or call 1800 333 000.

Feature image: Australian Missing Persons Register.