Proof of shoplifting can be shown with such things as: (1)the store video camera, (2)observations by security staff at the store, (3)witness testimony, and (4)statements made by the accused himself. Even if they didn't find anything on you, they may have observed you hiding merchandise somewhere else or with an accomplice. Also, shoplifting is not only leaving a store with unpaid merchandise. It can include switching price tags or eating food in the store and hiding the food wrapper.They need evidence. The question is what kind of evidence do they have that they can accuse you of shoplifting.