Rebecca vanished from a country fair 28 years ago. Her sister has never given up hope

Exclusive: For 28 years, the murder of Rebecca Richardson has remained a mystery. The 15-year-old vanished from a country fair in the Queensland town of Gin Gin.

One man admitted to witnessing her murder but she's never been found.

Her sister Jessica has never given up the fight to find her and is now telling Rebecca's story in her first TV interview.

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"This is the last place I saw my sister," Jessica Richardson told A Current Affair tearfully, standing in the exact spot at the Gin Gin showgrounds.

"It's hard being back here, it's hard thinking about it all over again, it's going to be hard dragging it all up but Rebecca deserves that. Rebecca should have got that in the first place in 1998."

It's a cold case you may have never heard of because the mystery murder of Rebecca Richardson has barely been reported on until now.

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"Why? Why is that? Why doesn't Rebecca deserve a voice?" Jessica questioned.

Jessica has never been able to bring her big sister home but Jodie Martin Stephen Van Der Vegt could hold the key to what happened to her.

Everyone knows Jodie by his middle name Stephen, and at the time, he was 23 years old.

He admits he buried Rebecca's body but claims it wasn't him who murdered her.

"Tell me where my sister is, tell us where she is!" Jessica pleaded.

A Current Affair can reveal a bombshell revelation from his family.

"We all know what went on," one family member told A Current Affair.

"Why did nobody tell me? Why did nobody call him out on it?" Jessica asked the family.

Gin Gin, west of Bundaberg, has been in the headlines recently for the alleged murder of Pheobe Bishop but there's another girl in the town who never came home.

I grew up in this small town, we all heard rumours about a teenager who vanished from a local fair but we've never been told the full story.

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"(Rebecca was) very outgoing, very courageous, charismatic, bubbly, bright, had a lot of potential, had a lot going for her, had her whole life ahead of her," Jessica described her big sister.

"We were like best friends, we did everything together, always together, always having fun and she deserves more than what she got, she deserves answers."

In 1998, when Jessica was 14 and Rebecca was 15, the sisters were at the Gin Gin Showgrounds for the town's annual Santa Fair, a Christmas celebration.

"We were with our friends, she was with her friends, I was with mine, and we were just going on the rides and having a laugh and then she came over and said she was off," Jessica recalled.

"She told me she was going with Steve up to our house to grab some belongings and I asked her if I could come with her and she told me no, she'd be soon."

"Does that replay in your mind over and over?" A Current Affair asked.

"Always, I wish I went with her," Jessica replied.

"Who was Steve to you guys at that point?" A Current Affair asked.

"I guess a family friend, someone that we trusted, his father and brother in law were helping my dad to build our family home," Jessica explained.

The teenagers and their father were only new to Gin Gin, and while they were waiting for their home to be built, they lived with Stephen's family.

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"This is the house where we were staying with the Van Der Vegts," Jessica said, standing out the front of the property.

"And where was Stephen staying?" A Current Affair asked.

"In a caravan on the same property," she replied.

The Richardson's hadn't been living there for long when tragedy struck.

"My dad had passed away only a month, just under a month, before Rebecca went missing and we were left here on our own," Jessica explained.

"Rebecca was planning for us to move overseas to live with family because our family is in England."

With their father gone, Stephen should've been someone the teenagers could trust.

"The level of attention that he gave her, it wasn't appropriate for a man of that age towards a 15-year-old girl," Jessica told A Current Affair.

Jessica thought Stephen was taking Rebecca home from Santa Fair but she was never seen again.

"I knew the next day that something was wrong. Two of her friends questioned him where she was and he took them in his car driving around looking for her, pretending to help them find her, when he'd already known what had happened to her," Jessica said.

Stephen tried convincing police Rebecca was still alive, telling lie after lie about her whereabouts.

"The police called him and asked him what his version of events were. They told him to write it down and provide that to them and slipped it under the police door when it was closed," Jessica explained.

"And that was the end of the line of inquiry, that was just accepted as what it was, that she had run off with her boyfriend to Brisbane and I told them that she would never do that."

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More than two years later, Stephen's then girlfriend told police he'd confessed to her that he buried Rebecca's body in a tip, just outside of Gin Gin.

"It's hard to be here," Jessica told A Current Affair, visiting the site for the first time.

"He's told so many different stories it's hard to know the truth."

Stephen was originally charged with murder but police accepted his offer to plead guilty to being an accessory after the fact and he was sentenced to eight years' jail.

"The decision not to attempt to find (Rebecca's body) was one which was made by the police," the judge stated.

After that, the case was closed and the question still remains, who killed Rebecca?

"There hasn't actually been any major searches here," A Current Affair said.

"Well you think if somebody showed you where they said they buried somebody then you'd have space to look," Jessica replied.

Stephen's been living in a dilapidated property near Rockhampton but he's recently back behind bars on drugs charges.

While we were in Gin Gin, we visited his family.

"My main itch in the back of my head was the car, why was the car attempted to be set on fire? It was completely stripped. It was sitting there down in the, basically in the riverbed, up there at Baffle Creek," one family member admitted to A Current Affair.

"That's the car and it was later said that Rebecca had been in."

The family member told us he saw the car Stephen had been driving, torched, soon after Rebecca's disappearance at a creek an hour north of Gin Gin.

"I'm of the belief she's up Baffle Creek," the family member revealed.

After years of fighting, Jessica's won her battle for a coronial inquest into Rebecca's murder.

It begins tomorrow.

"I know that Steve's the one that holds the key. He was there when Rebecca died. Help bring her home, now is that time," Jessica pleaded.