Hackett, a 1500m gold medallist at both the Sydney and Athens Olympics, was caring for his four-year-old children, twins Jagger and Charlize, at Crown Casino when he awoke in the early hours of Saturday morning to discover his son missing from his room.
Without either shoes or a shirt, the 33-year-old searched the corridors around his room before hitting the foyer in search of the boy.
Hackett, whose marriage to former wife Candice Alley disintegrated in 2012 after he wrecked his own high-rise Southbank apartment in a drunken rage, finally found Jagger safely in the company of Casino security guards.