This is going to bother me

I like working in a cafe or coffee shop because I can watch random people while I work, or take breaks from working. Today while I was working - 3 hours so far at the time of writing this - I saw a woman walk into the shop that I recognized. The problem is that I can't figure out where I recognize her from. She walked in, started walking towards a table, looked at me, and then turned around and walked out. The more I think about who she was, the more I realize I am not going to remember where I recognize her from. I'm not sure if she's someone I've randomly given food to on the street, works in a place I have gone to before, or just someone I've randomly watched pass by on the street. Maybe I've seen her from here too, since there seems to be a number of people who regularly come to this cafe. Either way, it was really strange to see her look directly at me and then turn around.