Nick Veljanovski was 28 years old when he was last seen at the Royal National Park in Bundeena between 12pm-3pm on June 11, 2014.
He asked directions from a park ranger and has not been seen since.
Sylvia has been searching for Nick, the practical joker of the family and someone who always had time for his family and friends, ever since and hasn’t let up despite her terrible diagnosis.
"Every time the phone rings, every time I hear the doorbell ring, a big part of me thinks it’s going to be Nick," she told Mamamia.
Sylvia said she hopes and prays for positive feedback or leads and has to take each day as it comes.
"I just miss him so much. As time goes by the pain only gets more unbearable," she said.
"We go through the theories on a daily basis, but we haven’t found anything and neither have the police. As a mother, I cannot accept that he is gone without any concrete evidence. There’s been nothing, nothing at all."
"People tell me ‘You must move on with life’, but I can’t do that unless I have some way of knowing. I can’t move on."
The family have found new hope from an unexpected platform: Facebook.
A campaign from Missing Persons Advocacy Network (MPAN) plans to harness the power of the social media site's new facial recognition and auto-tagging technology in the search for missing people.
The Invisible Friends campaign features Facebook profiles of missing persons, supported by a push to get as many Facebook users around the world to ‘friend’ these profiles.
It puts artificial intelligence to good use and by searching the backgrounds of each photo and video posted by the friends of each Invisible Friends profile, the initiative hopes to identify and locate these missing people.
Nick's younger brother, Jim, runs a Facebook page dedicated to his brother, who he is convinced is still out there somewhere, and is hoping the campaign provides some answers.
"The more people that like and share, the more likely it is that someone who has seen Nick - or knows something they haven’t passed on - will see it and get in touch," he said.
"It used to feel like this was something that happened to other people when I saw missing persons on TV, but now it’s us - it’s like a never ending nightmare. Police have never found Nick’s body or any kind of evidence, so we know he must be alive out there somewhere."
“We know that some key sightings of Nick were not reported to the police until weeks after he went missing, so we know it’s possible there are others who didn’t realise what they saw was important, or didn’t report for some other reason."
Facebook's facial recognition technology is more accurate than the FBI's, operating at an accuracy of 98%.
Each profile in the campaign has an active police report, and must meet other strict criteria.
Around 500 million photos and videos are posted to Facebook each day, and if one of the faces match, the Facebook algorithm will auto-tag the profile and notify MPAN of the missing person being identified in the image.
Nick is also being featured in MPAN's Unmissable Coffee Cups campaign, modernising the old milk carton campaigns.
More than 38,000 missing people reports are submitted to police each year in Australia. Over 98 per cent of people reported missing are located, and almost all are found alive and well.
This National Missing Persons Week runs from August 5-11, and aims to raise awareness of those in Australia who are still missing, and the impacts on the family and community of missing people.