If the beeper goes off while a person leaves a store who has not already been seen by Security stealing within the shop the approach of the Staff / Security to the person is generally along the lines of "oh, the tag may not have been removed properly, can I have a look and we'll take care of it now" its rarely antagonistic and therefore I can't imagine the shopper in question would have had a problem, after all who wants to arrive home with a lump of plastic attached to your purchase?