Gary Abell, 17, was last seen waving a yellow golf flagstick in the air as he staggered drunkenly along a lane after a St Valentine's Day party.
He was almost certainly heading for a nearby main road which led to the home of his former girlfriend. But he failed to reach his destination and the trail remains cold almost four weeks after West Mercia police began scouring fields and woodland around Redditch, Hereford and Worcester where he went missing.
Dozens of volunteers joined Gary's family, police and dog handlers on a week-long search. Divers dragged lakes and ponds in the area. Police were again searching yesterday.
Detectives say they are keeping an open mind, but Mr Abell, 48, fears his son's disappearance may be due to something more sinister.
He believes Gary has been abducted and is offering a reward for information leading to his safe return. 'There are just no clues - it's as if Gary has disappeared off the face of the earth,' he said.
'I believe he has been abducted and I'm convinced somebody somewhere knows something. Gary was perfectly happy at home and we had already started looking for a Ford Fiesta to buy him for his 18th birthday in May.
'Now I'm just praying he is still alive. I spend all day looking for him and cover the same ground over and over again.'
Gary lived with his father and stepmother, Ann, at the Lord Clifden pub, in Hockley, Birmingham. He played in the pub darts and dominoes teams and had planned to join regulars taking part in a fishing contest on the river Avon.
The day before he vanished, Gary, a trainee engineer, helped his stepmother prepare for a private party at the pub. At lunchtime he set off in his blue Mini for Redditch where he used to live.
Ironically, a week earlier he and his best friend Stephen Webb, 18, had left a Redditch pub shortly before a man was stabbed to death and they were due to make a statement at the local police station that afternoon.
His parents knew this but they did not know he intended to visit his former girlfriend Vicky Hitch, 17, on the way.
He turned up at her home in Alvechurch with a red rose and a valentine card. 'Gary was his usual self and we played on the computer then had a chat,' she said.
Gary and Stephen made their statements and met Arthur Fisher, 17, for an early evening drink in a Redditch pub. The three went on to a girl's 21st birthday party in Church Hill.
During the night they drank about 10 pints of lager, plus vodka and whisky. Gary and Arthur were involved in a minor scuffle shortly after midnight.
'We did have an argument but I don't even know what it was about,' said Arthur, a YTS hairdresser. He woke at dawn in the town centre and was able to recall little about the party. He has visited a hypnotist in a failed attempt to trigger his memory.
Gary left the party just after 1am and walked one-and-a-half miles across Abbey Park golf course where his cigarette lighter was later found. Three motorists then saw him lurch up Dagnell End Lane at 1.40am carrying the flagstick - a taxi driver had to stop when he saw Gary crawling in the middle of the road.
Police think he was heading for Vicky's home - he had walked there late at night before and slept in a garage or greenhouse.
But even though police later stopped 200 cars in a spot check on the Birmingham Road no one reported seeing Gary there.
Acting Detective Chief Inspector Steve Walters, leading the inquiry, said there were three possible scenarios to explain what had happened.
Firstly, Gary could have been in an accident as a result of too much alcohol. 'There is quite a lot of open land in the area and it could well be that in a few months' time when farmers get in their fields we will find a body,' Det Ch Insp Walters said.
'Secondly he could have wanted to go missing. He doesn't seem the sort of lad who wanted to run away but there could be something in his make-up we have not found.
'Thirdly . . . either he was abducted or maybe knocked down by a drunk driver who panicked and disposed of his body.'
Standing 5ft 11ins and with a powerful 13-stone physique Gary was capable of looking after himself.
But Stephen, a welder, who said Gary had no coat or money when he disappeared, believes he was so drunk he would have been easy prey for an abductor. 'Gary is as strong as an ox but we just got absolutely pathetic that night and he couldn't have defended himself.'