The two little girls were permitted by their carers - Kirste's grandmother and Joanne's mother and father - to go to the toilet together. Tragically they never returned, and their bodies have never been found.
After the event, multiple reports came in revealing the two girls had been sighted looking upset and in the company of an unknown man.
Their presumed murders are sometimes believed to be related to the Beaumont children's disappearance in 1966. The police sketch of the man seen with the two girls resembles that of the man witnessed with the Beaumont children.
Joanne’s sister Suzanne has never given up on finding her lost sibling, and getting some degree of closure for the families of the girls. She is speaking up in a bid to keep the crime in the public eye – hoping that finally the pieces will fall together, and there may be some movement in the case.
A man recently approached Suzanne privately to discuss what he saw, and the awful sense of guilt that has followed him ever since.
'The gentleman contacted me through Facebook, and he was so profoundly apologetic for not stopping that day,' says Suzanne of the man - who witnessed two girls matching the description of the missing children being led away from the oval in a distressed state.
Like other witnesses that day, he simply assumed the man who was taking the girls away was their parent or guardian, and assumed their distress was likely just trivial childhood tears and nothing more sinister.
'He says he's lived with the guilt every single moment of his life since that day. When he found out the following day what he's witnessed was potentially Joanne and Kirste, the guilt began eating away at him.
'But as I explained to him, he wasn't to know.'
Suzanne tells of the last witness accounts of her sister, 'It's heartbreaking to know that she [Joanne] was obviously upset. It breaks my heart to know that somebody could be so sinister to take two innocent girls.'
Throughout the podcast, Suzanne delves into the devastating toll the tragic disappearance took on her family life. Her father, who passed away in 1981, would stay up night after night searching and hoping for his daughter's return.
Suzanne recalls, 'After Jo disappeared, he would spend every available moment in his car driving around Adelaide just looking, hoping to find something, anything.'
South Australian law enforcement claim that 'even the smallest bit of information' will help them to uncover the truth.
The investigative podcast aims to shed fresh light on the 44-year cold case and explore what really happened.
In each installment, listeners will hear from family, as well as leading detectives and experts, to uncover the facts that have never been reported.
Listen to the series trailer below:
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Anyone with information regarding the disappearance of Joanne Ratcliffe and Kirste Gordon is asked to contact Crime Stoppers on 1800 333 000.