Wayne Magalogo, 65, simply thought someone had left a golf ball on the course, as he was playing a round at Mountain View, in West Jordan.
Instead, the much younger man -- who had hit the ball -- came up and punched Magalogo, while he was not looking.
The incident occurred early last month, and Magalogo didn't tell anyone about the incident, until he continued to have severe headaches.
Eventually the victim had to have emergency surgery, for bleeding on the brain.
West Jordan police are now hoping someone will call with information about the incident.