My confusion while working at a retail store

I was working a four-hour shift as a cashier at a retail store. When it was time for my break, a cashier named Mary replaced me. Before I went on my break, I needed to empty my trash and hangers. For some reason, within those few minutes, my brain got confused.

After I emptied the hangers, I went back to my register and I gave the cashier the hanger bucket. I looked at Mary and I said, “Oh, now you're here.” and she said, you said, “hi Mary”. “Who did you think I was?” I told her that my brain was a little confused. I thought that Emma had replaced me at my register. Weird! In my brain, I remembered another cashier coming to my register just minutes ago.