Australia's forgotten teens: The vanishing of Elaine Johnson and Kerry Joel.

Growing up in the '80s, it wasn't unusual for friends Elaine Johnson and Kerry Anne Joel to not return home.

The teenagers, who lived in NSW's Sutherland Shire, would regularly visit the arcade, ride bikes, and party with friends into the early hours of the night.

Sometimes, the only way to get home was by sticking their thumbs out and catching a ride with a stranger. There were even times when they slept in a park or on a train.

So when Elaine, 16, and Kerry, 17, didn't return home in February 1980, at first, no one blinked an eye. As days went on, and they still didn't return, they were labelled as runaways. Now, 45 years later, they are still nowhere to be seen.

But Elaine's sisters, Helen and Wendy, are determined to find answers. Along with Kate Kachor, the host of Out from the Cold: Searching for Elaine, the women are putting together the pieces from the disappearance, hoping to solve the puzzle.

Watch: The Police Officer Who Believed Her & Changed Her Life. Post continues after video.

Speaking to Mamamia's True Crime Conversations, Kachor explained the circumstances behind Elaine and Kerry's disappearance.

In early 1980, Elaine was supposed to join her family on a trip, but she decided to stay home. When her parents returned, they found their rental in a state of disarray. Beds were slept in. Rubbish covered the floor. Elaine had clearly had people over, and her parents weren't happy.

"A lot of emotions are running high at that point," Kachor told TCC host Claire Murphy. "Elaine was home at the time, and her parents had a talking to her, really sort of saying, shape up or ship out, and at the heat of the moment, she decided to leave."

From there, Elaine went to stay with a few different people. Her father picked her up and brought her back home, but she left again.

For Elaine's sisters, Helen, 12, and Wendy, 14, this was the last time "they can clearly remember seeing Elaine."

Around the same time, while Kerry's mother was at work, the 17-year-old had borrowed her car and gone on a joyride to an arcade called Flashes.

Through investigation, it has come to light that Flashes has been shrouded in controversy, with stories of seedy men preying on young girls.

"[Kerry] turned up, beeped the horn. And what we've been told is that Elaine and a third girl came out of Flashes and jumped in the car and then all three girls drove around the Shire looking for other friends," said Kachor.

Then, allegedly, Kerry "had a bingle" and damaged her mother's car.

"In a bit of a panic, because she was unlicensed, she took her mother's car home and took off, grabbed belongings and the three girls headed off. As far as we know, they headed back to Flashes."

Since then, Kachor has heard accounts that the three girls headed north. There have also been suggestions that they stayed in a caravan park, but nothing has been confirmed.

A few weeks later, when the girls had still not returned home, Elaine and Kerry's family reported them missing. 

"We don't know the exact details of exactly when they disappeared. It seems to vary depending on speaking to friends of the time and the family," said Kachor.

But the police documentation from the time is incomplete. Whether that is due to human error, Kachor doesn't know.

"From what we sort of gauged, it was more a case that Elaine and Kerry were treated as runaways," said the podcast host.

"If someone's reported missing, you should at least have a file that says they were reported missing on this particular day. As far as the family are aware, for Elaine, she was treated as a runaway, and there is no file for her. There is a file now, but back then, the crucial time, there wasn't one."

Listen to the full episode below. Post continues afterwards.

Elaine and Kerry's friends, and key witnesses, also weren't interviewed by police until 2015. By then, their memories weren't great.

"Imagine your friend disappears in 1980 and three decades later you're asked, 'Oh, can you tell us what you remember from that time?' It's an incredible amount of time, and it's just a small part of Elaine's story, and particularly Elaine's sisters Helen and Wendy's story trying to search for her."

Over the four decades since they have been searching, Helen and Wendy have heard many theories that might lead them to their sister Elaine. One was that their older sister had changed her name to Crystal and was working as a sex worker.

"Wendy had a friend over one day to her house, and this was years and years after Elaine had been reported missing," said Kachor. "They were in the lounge room talking, and this friend turned and said, 'Oh, I know her,' pointing to a photo of Elaine. 'That's Crystal.'"

Wendy assumed her friend was mistaken, but they insisted they recongised her.

So, one night, Wendy, Helen, and Helen's husband Joe visited the brothel district of Newcastle and went door-to-door, searching for any information about Elaine.

"They showed a photo of Elaine, the same photo that the friend had identified as Crystal. And, from what Helen has told me, people within the brothel said, 'Oh, yes, Elaine'. They used her name as Elaine and then referred to her as Crystal," said Kachor.

"And so with that information, they thought 'Okay, well right, let's go to the next one,' and a similar thing had happened, and they were told that Crystal was on a six-week run. She wasn't currently there."

They left with a glimmer of hope, but then things went silent. Until Helen got a phone call.

"It was someone who said, 'Hello, I'm Crystal. I wish I could be your sister, but I'm not,'" Kachor recalled.

Later, however, a woman came into Helen's workplace to "tell her to keep looking."

"The thing about Helen is she just keeps going, she's hit a lot of brick walls in her search, but it doesn't stop her searching."

The sisters have also asked the NSW government to offer a reward for information about Elaine and Kerry's disappearance, but have been denied.

Going into the podcast, Kachor never expected to solve the case, but feels lucky to help Helen and Wendy in their search.

"I'm just in a very fortunate position to be able to help get their story, much of it is very untold," she said. "What they really want is people to come forward. Even the smallest bit of information makes such a huge difference."

Feature Image: Instagram/@helpfindelainejohnson