It took less than half an hour after a be-on-the-lookout advisory was issued for Grass Valley Police officers to find and arrest three suspects in an Auburn armed robbery. Auburn Police officers had responded to the call at about 7:15 p.m. Wednesday on Grass Valley Highway, said Auburn Police Sgt. Rick Hardesty. The victim told officers he had been robbed at gunpoint of cash and a cell phone by two men, who also had assaulted him with their guns. “He recognized the vehicle as belonging to his ex-girlfriend,” Hardesty said. The Auburn Police Department issued an advisory just before 8 …