It's been almost three years since Donald (Donny) Govan went missing from an Echuca campsite in 2012, but his family have not given up hope.

As National Missing Persons Week rolls around, Donny's sister Rachael O’Keane holds out hope the campaign will help build awareness of her brother's case.

“Keeping his photo and story out there for people to see and refresh their memory that he is still missing will help,” she said.

For Ms O'Keane and her family, a day hasn't gone by when they haven't thought about the whereabouts of Donny.

“It does cross your mind every day,” she said.

“We haven't had that closure, we don't know if he is alive or dead.

“We're trying to move on with our lives. We've tried our hardest to find him but we can't find a trace of him.

“But we're never giving up.”

Donny, then 16, disappeared on September 1, 2012, from an Echuca campsite where he had been camping with Ms O’Keane and four Ballarat friends.

After a few drinks, Donny became paranoid about his fellow campers, claiming they were out to get him, and ran off into thick bush.

Despite a manhunt following Donny's disappearance, there has only been one credible sighting of him since, when an elderly woman living 10 kilometres from the campsite said a well-mannered boy matching Donny’s description appeared from the bush and asked her for breakfast a few days after he disappeared.

She told police the boy said he had spent the night in the bush and was planning to go to Bendigo.

Ms O'Keane said the upcoming National Missing Persons Week was a good chance to revitalise the search for Donny who is described as a 173cm tall teenager with light brown hair.

“If people don't hear about things for a while they assume he has been found. This keeps it out there, no matter how much time passed we will never give up on Donny.

“Someone knows something, they have to say something.”

Donny's case has recently been one of 18 stories to appear in the new book Unsolved Australia by author Justine Ford. Terrance Floyd who went missing in 1975 and Sherrlynn Mitchell who went missing in 1973 are also still missing.