The incident occurred when the robber punched the deputy before making off with cash and a cellphone, a spokesperson for the Santa Ana Police Department said.
The deputy was reported missing about 4 a.m. Sunday by a friend who told police that another person had answered the deputy's cellphone.
The deputy drove away from the scene and returned about 90 minutes later, police Sgt. Sergio Gutierrez said. There, he was interviewed by investigators.
"He does have some minor injuries that looked like he was punched," Gutierrez said.
No description of a suspect was provided.