I worked at an Antique Mall that had a policy that we had to show the inside of our bags, purses etc. It didn't really work. One gal (I am almost positive) stole sterling and gold charms from locked cases and they were so small that she could stick them anywhere.
Another gal we thought had devised some bag under her skirts to carry things...she was heavy and wore gathered skirts a lot and sometimes walked funny. Now these were never proven, but could have happened.
I know it is sad that companies have to make these tough decisions, but it is part of our reality.