One of the three men who went to Darcy Mills' aid had his new ute stolen as he was chasing the 14-year-old along busy Rosamund Road in Maidstone on Tuesday.

Jennifer Mills said her 14-year-old son Darcy sneaked out of the house before he jumped the fence at their home in West Footscray and fled down the street on Tuesday night.

Ms Mills said she did not realise Darcy had disappeared until a neighbour saw him running down the street and knocked on the door to tell her.

"He's just so quick and ambulant," she said. "Within a few seconds he was out of sight."

Ms Mills said she called the police, but by that time Darcy had already reached Maidstone.

He was sprinting through the middle of streaming peak-hour traffic, cars swerving and slamming on brakes to avoid him.

She lauded the bravery of three motorists who saw Darcy on the road and stopped their cars to help him.

They kept him busy by throwing balls on a nearby tennis court while they waited for police to arrive.

"Fortunately some good Samaritans noticed him behaving oddly because he was weaving in and out of traffic and not noticing any of the traffic, and they stopped," she said.

"He's quite a big boy and a lot of people wouldn't have stopped. He looks normal but he doesn't have any road sense whatsoever and we are just so indebted to those guys."

When asked whether she believed those three men saved his life, Ms Mills said "absolutely, not a question in my mind."

"Cars were travelling at speed, he was in the middle of the road, I just can't imagine how he wouldn't have been hit," she said. "He just doesn't have that alertness to know that he might get hit by a car. It was a life-or-death situation."

Ms Mills said her home was modified for Darcy's special needs, but one of the locks wasn't completely deadlocked on Tuesday night, allowing him to escape outside.

"It was an oversight and it is so lucky a quick-thinking neighbour saw him," she said."But he is the master of escape. He has no physical disabilities so he was just off down the road as soon as he got out."

She said she was devastated to hear one of the good Samaritans had his ute stolen as he ran to rescue Darcy.

"Clearly [the thieves] were taking advantage," Ms Mills said. "There would have been a lot of fuss with what was going on ... but I'm more focused on the fellas who saved Darcy. They are the heroes for me."

The good Samaritan's ute- along with his house keys, wallet and laptop -were stolen.

The thieves managed to rack up a couple of thousand dollars worth of transactions before the man reported his cards stolen.

Ms Mills said the family was "frantic" during Darcy's disappearance. She described him as a gentle and loving boy.

"He is lovely, he's bubbly, he's affectionate ... but he's completely oblivious to any dangers of the world," she said. "He has the language of a two-year-old and he might look a bit scary but he's really just the most harmless and innocent boy."

Ms Mills said she hoped the incident would raise awareness about the plight of people with disablities and their families.

"It's really heartening for us as a family, just struggling away, to know there are good people out there willing to step up and take charge when something like this happens," she said.

"They just threw themselves in there to save him. They're just amazing people."

A 51-year-old North Melbourne man has been charged with two counts of theft of motor vehicle, theft from motor vehicle and four counts of obtain property by deception.

He has bailed to appear at the Melbourne Magistrates Court on April 12.

A 41-year-old man and a 34-year-old man, both from Maidstone, were also been arrested then released pending further inquiries.

with Robyn Grace