Mr Pearce, 21, was last seen in North Wollongong on Tuesday night but tried to call mother Jo-Ann on Wednesday morning.

Since then, his family have not heard anything from him, which Jo-Ann said was out of character.

"Every day, there's a phone call, a Facebook message or a text message or something," she said.

"It was nearly every day."

The lack of contact combined with the fact that his social media accounts have been untouched has led Jo-Ann and husband Gary Pearce Sr to fear the worst.

"If he's in the area someone's holding him and they won't let him out, they've got him somewhere," Mr Pearce said.

"He wouldn't be in the area of his own accord, he wouldn't be able to keep quiet. He'd have to see someone, he'd have to talk to someone, he'd have to be on social media."

Ms Pearce believed 21-year-old Gary was no longer in the Illawarra.

"I have a gut feeling that he's not in the area and he's crossed somebody he shouldn't have crossed," she said.

"That he's somewhere else. That's how I feel, call it a mother's instinct."

She described him as "loveable" man with "a kind heart", but who could also be taken advantage of.

"He's lost his way a little bit, got in with the wrong crowd but he's always stayed around the family, especially me and his brother William," she said.

The family have been using social media to help find Gary and are also putting up flyers around his local haunts in the hope it might jog someone's memory, get someone to come forward.

"I honestly believe something unforeseen has happened to him," Ms Pearce said.

"Somebody has to know something. I don't understand how someone can simply vanish.

"Somebody has to know something but they're keeping their mouth shut so they don't get in trouble. That's what I think."

Gary is described as being of Caucasian appearance with an olive complexion, 165cm-175cm tall, with a medium build, brown hair, and a beard and moustache.

He was last seen driving a white VY Commodore wagon with damage to the left-hand back bumper.

He also has several distinctive tattoos, including one on his skull that reads "Ruthless" and two on his neck - one featuring dollar signs and the letter M and a second featuring the Minions cartoon characters.

People with any information are asked to call Lake Illawarra Police on 4232 5599 or Crime Stoppers on 1800 333 000.