"Somebody has taken him" was William Tyrrell's foster mum's instant feeling when her little boy couldn't be found, a Coronial inquest has heard.
William disappeared from his grandmother's front yard in Kendall on the Mid North Coast in September 2014 while playing "daddy tiger" with his sister.
No trace of him has ever been found.
His foster carer, who cannot be identified, spoke of her terror when she realised it was "too quiet" and the three-year-old could not be found.
"I was driving to Port Macquarie airport to collect a family member and had this flash of [realisation that] there were two cars," she said, adding she had forgotten about it in the panic of William's disappearance.
"I just went, 'There were two cars there'. My heart just sank because I thought those two cars were there for both of them," she said.
"I got back to the house, I went straight down to the command post and I told the guy on duty. He gave me his phone and said search for the cars."
William's disappearance sparked one of the state's largest police investigations to date, which has uncovered a group of North Coast paedophiles, investigated 600 persons of interest and combed through over 15,000 pieces of evidence.
Nobody has ever been charged with his disappearance.
Detective Chief Inspector Gary Jubelin, who was until recently the officer in charge of the investigation, told reporters last year that his team had concluded his disappearance was most likely the result of "human intervention".