Patrol cars swarmed the end of the street in minutes and officers got under way searching surrounding properties and a nearby gully, as well as waterways.
Avery's identical twin brother was dressed in a matching blue onesie and grey trackpants and a photo of him was shared by police to notify the public if they saw him.
Because of his condition, Avery does not respond to his name so is harder to find, his mother said.
"He gets fixated on things so we didn't know where he would be and what he'd be doing."
Police officers were seen searching every driveway, checking in and around gardens.
"It's a long time to be missing," Ms Reynolds said, "especially because he's so active so he could be quite far away".
As the time stretched on, she got more and more worried, she said.
When Constable Schuster brought the little boy back snuggled in her arms, Ms Reynolds was "just overwhelmed".
"The police did an awesome job. We're so thankful ... I just can't speak highly enough of them."
Ms Reynolds also wanted to thank all the neighbours for rallying together for the search.