Jason Kemp of Nerang said he had only picked up the hobby of metal detecting about three months earlier when he went searching in the lot that formerly housed the apartment building.
He found the gold ring, engraved with the couple's first names, under about 8 inches of dirt.
Kemp posted a photo of the ring to the Gold Coast Community page on Facebook, where it eventually came to O'Brien's attention.
She messaged Kemp with details of the ring and the location where she lost it, making the finder confident that she was the rightful owner of the item.
O'Brien said she now plans to give the ring to her granddaughter as a family heirloom.