Ian Draper witnessed a murder and was likely killed as payback.
Police say there is no other explanation for how the loved and law-abiding man from Minto, in south-west Sydney, disappeared 20 years ago.
Today a $100,000 reward was increased to $1 million for any information on his suspected murder.
READ MORE: Underworld figure Andrew Perish released on parole
"Ian Draper was a hard-working man, had no criminal record, had no issues whatsoever," Detective Superintendent Danny Doherty said today.
A colleague was the last to see the 37-year-old bartender alive, leaving the car park at Mounties in Mount Pritchard in the early hours of August 3, 2001.
Six weeks later, Mr Draper's Ford Falcon was found in Leppington, dumped outside a Rebels bikie clubhouse.
It had been wiped clean, leaving detectives with no forensic evidence.
The only possible explanation for Mr Draper's disappearance was a fatal bashing he witnessed while working at a Liverpool pub in 1995.
He gave evidence against underworld figure Andrew Perish.
Perish was cleared of that murder, but he and brother Anthony went on to plot and dismember police informant Terry Falconer - a crime which later became an Underbelly series.
"That's obviously one of the lines of inquiry we'll be looking at," Detective Superintendent Doherty said today.
Mr Draper's mother Janet said she misses her son "more than words can express".
"Last week was Ian's birthday and we have now spent 20 years without him, missing out on celebrating these milestones and many other special family occasions," Ms Draper said.
"Ian was a loving son, brother, uncle and friend and taken far too soon.
"If anyone in the community has any information at all about what happened to our son or can help locate his remains, please, please, contact the police."
Anyone with information is urged to contact Crime Stoppers on 1800 333 000.
