Years ago our cat vanished. We assumed she'd been run over (lived in a busy city) and rang round every rescue and the RSPCA in particular, every single day. Every day I asked if a little black and white cat from x area had been brought in. Every day they categorically said no - no cats brought in, none in our hospital from that area, or that fit that description. After 10 days my son (then about 5) read a postcard in a window in the next street that asked anyone who had lost a little black and white cat to knock on their door. Turned out they had been in the car behind some boy racers who knocked her over and drove away. They rushed her to the RSPCA. They fell in love with her and said if no-one claimed her, they'd re-home her.
So all the time the RSPCA lied to us on the phone (their hospital area was just behind the reception - would be no way anyone answering the phone couldn't know there was a small black and white cat admitted from x area on x day). They'd 'sold' her already so pretended she wasn't there.
I rang them, told them this and shamefacedly they admitted they did indeed have her.
The little cat is now 20 and still going strong. (She wasn't microchipped - less common in those days, but she had an ID tag that had fallen off her collar).
OP, I hope you track him down and pass on the info.
The irony with our cat was, the people who had offered to buy her from the RSPCA lived about 100 yards as the crow flies, from us. The day they paid their £50 and brought her home - she'd have walked right back home to us anyway (minus one leg). So they'd have lost their £50 and the cat and they were lovely people.