According to police, the last positive sighting reported of his son was at Mr Condren's business.
Phil Cowan's vehicle was later found abandoned near Bulls. Police suspect he was dumped in Tangimoana Forest.
Mr Condren and two others were arrested 16 months later. They pleaded not guilty to a charge of murder and were freed when a judge decided some evidence had prejudiced a fair trial. They cannot be charged again.
Mr and Mrs Cowan had written to all three, and were not unexpected by Mr Condren, who was "talkative" and friendly, but who denied any knowledge of the disappearance and who offered nothing to help bring closure.
Their second visit came as they questioned what he had told them first time, but the outcome was the same.
Their distress and another desperate plea were highlighted in a TV3 60 Minutes documentary last night, and Mr Cowan told Hawke's Bay Today: "It is one of the key aspects, that we're still trying to find Phil, admittedly with not a huge amount of hope.
"In this situation, I think you do all you can, follow all the processes, everything we can possibly think of, but after 10 years we still have nothing."
To try to extract something positive, he has committed to trying to find answers to underlying society issues which led to his son turning to drugs, which appears to have cost him his life.
Police Eastern District crime investigations manager Detective Inspector Ross Pinkham said such cases were reassessed from time to time, some based on new calls from the public.
While police had to keep open minds, the fact no body had been found indicated homicide as more likely. Recent arrests highlighted that in every case there remained some chance, Mr Pinkham said.
- APN