I have the same issue. If you don't look exactly like I expect and you're in the same place I expect then I can't really place you. I can see friends at the grocery store and have no idea who they are.

A friend of mine cut off her hair and dyed it. I saw her out and she said hello. We talked for a minute and I had no idea who the hell she was, so I politely excused myself thinking it was just someone I had met once or some drunk person striking up a conversation. Later that night I texted her and asked where she was. She walked up to me and asked what I needed. That's the only way I put it together.

I have never told her this.