Sometimes people who work at retail stores have these things called "breaks." On their breaks, they sometimes leave the back room to walk around the store or even leave the store.
When they are walking through the store, they are not available to help customers because they are ON BREAK.
Sometimes I understand when people don't get this. For instance, if an employee still has his or her name tag on, I can understand someone asking him or her a question.
But here's my thing. Even if they still have their name tag on, they almost always have something in their hand. Whether it's their phone, keys, wallet, etc., they will generally have something on them to signify that they are not on duty at the moment.
It's easier for me to avoid this because I work at Old Navy and don't have a uniform, but I was in Kroger the other day and saw a customer stop an employee to ask her a question. The employee was wearing her Kroger shirt, but she was talking on her cell phone and had her keys in her hand. Like, come on, lady. She's clearly not on the clock. Find someone who is to help you.