An autistic teenage boy who was reported missing in northern California years ago has been found shivering outside a Utah petrol station before being reunited with his family. 

Connerjack Oswalt was 16 when he wandered off from his family home in Clearlake, north of San Francisco, and vanished in September 2019. 

He was 19 when he was found about 1200km away and in another state this month. 

Oswalt was identified after a "concerned community member" reported seeing a man sleeping outside a petrol station in Park City, west of Salt Lake City in Utah. Police responded to the call on April 9, the Summit County Sheriff's Office said in a Facebook post. 

"This morning, he's very cold, he's shivering, he's obviously had a rough night," Sheriff Justin Martinez said of the man's condition that day. 

Police asked the man to sit inside one of their vehicles to warm up and began researching who he was, the sheriff's office said. In recent weeks, community members had been reporting an individual in the area who had been seen pushing a shopping cart. 

Oswalt, who has been diagnosed with autism, reportedly had a history of running away. 

"Through past interactions and the Saturday interaction, it was clear to deputies that the man communicated differently," the sheriff's office said, and also included an autism awareness hashtag on its Facebook post. The man, while not aggressive, refused or was unable to provide his name, according to authorities. 

A dispatcher started looking through pages on the National Centre for Missing and Exploited Children website and eventually came across a missing poster for Oswalt. 

"Deputies began making phone calls and were able to make contact with Connerjack's mother," Sheriff's Lieutenant Andrew Wright said. 

His mother told authorities Oswalt had a distinctive birthmark on his neck. Deputies found the mark on Oswalt, Wright said. 

Though authorities had previous interactions with Oswalt prior to that day, he had not shared who he was, Wright added. 

"Each time deputies interacted with Connerjack, he didn't provide any identifying information. 

"We had no reason to demand that he identify himself on the previous encounters because he was not violating the law. However, deputies offered Connerjack resources such as transportation, food, etc. He refused all offers made." 

Oswalt's mother Suzanne Flint told Fox 13 News she "never stopped looking" for her son. 

"There wasn't a day I wasn't searching for him, in some form or fashion," she said. 

In one of two bodycam videos released by the sheriff's office, Oswalt's stepfather is seen exclaiming in disbelief as police show him a mug shot of Oswalt to confirm it was the same person. 

Connerjack Oswalt can be seen on police Bodycam footage sitting outside the Park City store when he was found on April 9 2022. 

"Is it him?" Oswalt's mother can be heard saying on speaker phone. 

"A little bit older, but yeah," Oswalt's stepfather responds. 

"My sweetheart's alive," the mother is heard saying, while sobbing on the phone. "Can you go get him please?" 

Oswalt's stepfather and grandfather then travelled to Park City, Utah, to identify him in person and be reunited, Wright added. 

Investigators are still unsure how he ended up in Utah. 

"This remains the big question," Wright told USA Today. "Where did his journey take him over the past two and a half years? We suspect he didn't give identifying information because he was scared of police." 

- by Megan Palin, news.com.au