By the phone number, by someone seeing you rip off the slip and put it in your pocket. What if the DM or RM is in the office and just happens to look at the security camera, when you do it. Maybe you forget to block your phone number?
No, but we tell customers to put all 5's in the survey and we bribe them with free candy. I don't know why anyone would call from their home phone #? Just call from a pay phone.