Is this common in the US? (retail workers being searched)
I don't know about in the US, but in Canada, I used to work at Forever 21—a California-based retail chain—and you are required to go through a pat-down right before you leave the store. You'd have to look for a manager, and ask them to escort you to the front of the store, and have them pat you down.
Didn’t seem to help them. They filed for bankruptcy.