If it is only a few odds and ends that were missed while going through the store I don't see the big deal. The problem is when someone brings while shopping carts.
I'll never forget when we went Pesach shopping about 15 years ago in KRM, we got to the line with about 7-8 people ahead of us - an easy hour+ until our turn, by the time we were third in line this guy came over and asked if he can cut in front of us since he only had few items, naturally we said yes, he left the cart with his Son and proceeded to overfill it and bring another overflowing cart. The Chutzpa of some people!!!