His father Chris was on the back deck and had only hours earlier stopped Xavier from trying to open the door and play out the front.

"He pretty much learnt that morning how to open the front door, and I spent most of the morning chasing him up and down the hallway, so we were just keeping an eye on him," Mr McLachlan said.

"Jah came home from work, I was on the deck, and she came screaming 'he's gone'. The door was open and he'd let himself out and gone on an adventure."

It is every parent's worst nightmare, but the fact Xavier is non-verbal and has autism had the McLachlan's fearing the worst.

"He's got no sense of road safety, and rules, you can't tell him 'don't go over the fence'," Mrs McLachlan said.

"It was just panic, instant panic," Mr McLachlan said.

"I just took off straight down the road. I walked down the street looking in every driveway, every yard, until I got to the end of the street and I saw someone and asked if they'd seen a little boy walk past and they said, 'no'.

"I headed back home and we rang the cops to get them here as quick as possible and it was a matter of ringing everyone we knew, everyone that was close, to just help us look."

The McLachlans of South Launceston were frantic. After calling the police they began contacting whoever may have been able to help.

They said within half-an-hour three police cars, a motorbike and their closest family were ready to start searching for Xavier.

Over the course of the next 30 minutes, after Xavier had been gone for close to an hour, nearly 100 people had rallied to help find the lost little boy after a number of posts went out on social media asking for help.

"Family friends and strangers had seen the post, gotten in their car, and just came straight here. Half of them just started searching the blocks around the surrounding areas," Mr McLachlan said.

One of those strangers was Chloe Knight.

"[The fact he was missing] was shared on my Facebook and I went to my partner and said, 'we need to look for this little boy'," Ms Knight said.

So they jumped in the car and pledged their services to help find Xavier.

After close to three hours of him being missing, Ms Knight finally tracked him down.

Whether it was by fate, or through women's intuition, she headed to nearby Rose Lane - a woody thicket about one kilometre from the McLachlans' home and across a busy road.

Ms Knight said she was about to leave when she heard a child's whimper somewhere in the bushland and rushed towards the sound. She was still unable to see Xavier until she called out to him saying she could take him to his mum and he finally emerged, shoe and pant-less.

In the hurry to return him to his family Ms Knight slipped on a hill and cut her leg open. Despite his ordeal, Xavier reassured her it would be okay.

"He just saw my face and looked at me and said, 'are you okay?' and it was just very overwhelming," Ms Knight said.

From there Ms Knight rode with him in a car and delivered him back to the McLachlan home.

The news that Xavier had been found had already filtered through to the McLachlans - they were overcome with emotion.

"The car pulled and I just grabbed him straight away and he hugged me super tight. Then as soon as her saw his mum he pushed off me and just wanted her," Mr McLachlan said.

Sobbing, Mrs McLachlan grabbed her little boy and held him tight.

"He's not a cuddly kid, he doesn't do cuddles, so it was really nice to have him wrapped up. [I was thinking] 'I don't care if you want a cuddle or not, you're getting it' - but he let me cuddle him and then he wouldn't let go," she said.

Though the raw emotion of having their boy back overwhelmed them, the McLachlans were equally taken aback by the spirit of the community to help out in the rescue mission.

They said they had friends come and help from all over, and that in the end about "half of Launceston" was looking for Xavier.

Mr McLachlan said the response was tremendous.

"I remember just standing out the front and getting inboxes on Facebook from people I knew and didn't know asking what they could do to help or where they could start looking. I was just getting through some of the messages and we got the call that he had been found and he was on the way back here," he said.

Mrs McLachlan said it was like a scene out of a movie where a whole suburb bands together to search for a lost kid. She said, standing on a hill behind their house, she could see all of the helpers scouring the area and hear them calling 'Xavier'.

"I tried not to cry but he had been found by then and I just saw how genuine these people were about finding him, they actually cared about the fact my son was missing," she said.