Store checkout item separators

You know when you are at the store checking out, and your items are on the conveyor belt? Well, you put that little separator bar behind your stuff so that the cashier knows where your stuff ends and the next guy's begins. Today, after they cashier rang up my items, he put that little separator away. I said, "Hey, I wanted to buy that." He stopped and stared at me because I said something that was outside of his normal daily routine; something that he had not learned during indoc week. He had no idea what planet I was from or what language I was speaking. Let's just suffice it to say that I got to enjoy that little joke by myself. On another note, let's say you are at the store where store managers go to buy those separators; how does the cashier know where one guy's separators end and the next guy's begins? I guess they put groceries between them.