Land Search and Rescue teams and the Police Eagle helicopter spent days combing bush and farmland in the area with no luck.
But after four years police now hope to bring closure to Hayward's wife and children.
Detective Sergeant Andrew Saunders said new information suggests Hayward was the victim of a hit and run, probably accidental, but the driver "panicked and then disposed of his body".
"This has been a difficult time for the family of Mr Hayward," Saunders said.
He said it was unlikely that the driver had kept the accident a secret for four years and someone probably has information that would lead to the case being solved.
Locals or visitors who used Old Mountain Rd are being asked to think back to the beginning of spring, almost four years ago.
They may have seen someone driving dangerously, or a damaged vehicle - or someone may have talked about the accident.
On the programme Hayward's wife Kate recounted her last conversation with her husband.
He had called asking if she wanted to go to the family's bach but she declined, saying she had to work.
When his car was found abandoned, "I knew right away that something terrible had happened. I knew that that conversation...was our last conversation," she said on tonight's programme.
She begged anyone who knew something to come forward to police.
"I would hope that they would have the courage to speak out. it would mean so much to us."
Anyone who can provide information is asked to call Hamilton Police on 07 858 6200, or contact Crimestoppers anonymously on 0800 555 111.
