William Tyrrell's foster-father has detailed his frantic search through buildings and bushland immediately after the little boy disappeared.

William went missing from his foster-grandmother's front yard in Kendall on the Mid North Coast where he was playing on September 12, 2014. He was wearing his Spider-Man costume.

William Tyrrell, who went missing while playing in the garden of his foster grandmother's home in 2014. Credit:NSW Police

Despite an exhaustive search, which turned into a criminal investigation that focused on "human intervention", nobody has been charged and no trace of the boy has been found.

The foster-father, who cannot be identified, told a coronial inquest that he arrived home to his frantic wife, who asked if William was with him.