Russell Bohling was last seen by his family three years ago today when he left home in West Ella, near Hull, to drive to Bishop Burton College, near Beverley.
It is not clear whether he arrived and his car was found abandoned 45 miles away at Bempton Cliffs nature reserve, near Bridlington.
His family had already given up hope of seeing him alive again, but believed they may finally get some answers when they attended a second search of a former RAF bunker at Bempton this week, which Russell had looked at on his computer shortly before going missing.
Although the family were bracing themselves for the possible discovery of his body – having been unhappy about the extent of a previous search of the site in the immediate aftermath of his disappearance – a more thorough examination by firefighters on Wednesday also drew a blank.
His father Roger now admits the search has “run out of road”, and says the prospect of never getting closure is difficult to bear.
“It’s established that, and we needed to know, whether or not his body was there, so we know it’s not,” he said.
“We were present in the command vehicle when the search was being conducted and it was done properly this time – they lit the whole bunker, they used seven men, and it was all properly briefed beforehand; they were even looking for his missing car keys, it was that thorough.
“That’s not where his body is so we can forget about Bempton.
“We’ve got nowhere else to go – what do you do? The only hope now is for someone to come forwards, and they haven’t come forwards in three years so they are not likely to now. We are sort of just resigned to being one of those families that never knows.”
He added: “Our objective was to find Russell’s body and reunite it with the family and have a ceremony and close the book, but we can’t close the book so it’s hard. We just hoped for a time where we could get to a point where we could have a resolution and that’s just not going to happen. It’s emotionally very difficult, we are all pretty low.”
Mr Bohling said the family were now experiencing the trauma suffered by others whose loved ones have disappeared without trace.
But he also marked the anniversary by making one last appeal for anyone with information about his son’s disappearance to come forward – particularly in relation to a missing computer device, or memory stick, believed to have contained information about the underground bunker.
He said: “Whatever answer there was going to be from the search it was going to be difficult.
“It’s just one of those mysteries that happens to families – someone leaves in the morning and disappears; what do you do? You can only do your best to find them and when you run out of road you are just left with nothing, so we are through.
“The only thing we can hope for is if someone knows who gave Russell that USB device, if they can three years later bring themselves to come forwards to enable us to identify that person and see if they know anything about what happened to Russell, that’s really going to be the only way forward.
“One final thing is a request to the public – if you know who might have given Russell that USB device, even if you think you know, then let the police know.
“Russell didn’t find out about the bunker online; the police say he put a USB device into the computer and downloaded the information from the USB and they’ve never been able to find out where the device came from and it’s never been found.
“Whether or not he gave it back to that person we’ll never know. That’s the only way forwards – who was that person? If anybody has any idea thinking back over these three years, if they can just come forward...”
The former RAF radar station, a relic from the Cold War, had long been linked with Russell’s disappearance after it emerged he had studied the site on his computer.
His father believes Russell was not interested in its military history, but in a series of erotic pictures connected with the occult which have been painted on the walls.
Police believe the most likely explanation to his disappearance is that he had an accident or killed himself, but his family suspect someone else was involved.