Is this situation cheating?
Imagine your girlfriend uses one of those vibrator with a remote control to have some fun with herself,, but she loses the trigger while walking at the mall. Some time later, a man finds the controller on the floor and brings it home. He doesn't know if someone is using it, but he turns it on sporadically every day, just in case. Your girlfriend doesn't know who has the controller, but she doesn't remove the vibrator because she enjoys the taboo situation.