When I checked about punching my older child's card, they said that was the sign of charging privileges being removed(they had just punched my younger children's cards) I said wouldn't the machine just pick it up that he could charge and the CM said no....punched car=no charge. Some here have reported the same line I got, others have reported that they punched with no problems.
If you want to put it around your neck, you can get a plastic sleeve (like an ID holder or fishing license holder) and put the car in that attached to the thing around your neck.