我怎么觉得你就是偷东西的? Me too!

I owned store before. All securities trained to know when to stop someone (must have eye witness, video surveillance).
In most time, it's hard to make a case for less $100. If you are not a first timer, best bet is to kick you out and make sure you not come back again.
Store checking bag is normal (Homedepot dose). If people all like you, we have to live like in China - NO BAGS WILL ALLOWED IN STORE!