The small gold-plated tray was attached to the $20,000 George Adams (Tattersall) Handicap won by Mr Ay Bee at Riccarton in April 1979.
Bruce Jenkins found the trophy when removing a wall in his home at Henderson St, Wingatui, during alterations. The trophy was in a flat wooden hinged box.
"I took a wall out and I was scooping out the `Insulfluf' (insulation material) by hand when I felt this object," Jenkins said.
"I yelled out `I have found the hidden treasure'."
The house was formerly occupied by Tony and Lyn Prendergast, who trained Mr Ay Bee. They shifted to West Melton in 1983.
Tony Prendergast was surprised and delighted to have the trophy returned this week.
"It went missing and we didn't have a clue. It troubled us for years how it went astray," Prendergast said.
Mr Ay Bee is the best horse trained by Prendergast, who raced the Showoff-Gold Cross gelding with Ian Lomas and Dave Sims.
The George Adams Handicap was one of five straight wins for Mr Ay Bee as a 5yr-old. He carried top weight of 58.5kg to win the 2000m race.
Five days later he won the Great Autumn Handicap (2500m) at Riccarton with 60kg.
Earlier that season, he won the Dunedin Gold Cup.
He was ridden in his wins by Michael Mein.
Mr Ay Bee won the Kurow and Amberley Cups and Great Autumn Handicap the previous season.
Transferred to Takanini trainer Ray Verner as a 6yr-old, Mr Aye Bee won the 1979 Avondale Cup and King's Plate at Ellerslie.
Jenkins, the divisional manager of the Foundation Year at the University of Otago, rode horses in work for Prendergast as a teenager. He has since trained his own horses.
He has eight horses in work. They include a 2yr-old gelding by Personal Escort from Nzoom, a Dance Floor mare he prepared to win a maiden race at Oamaru six years ago at odds of 89-to-one.
