Blast from the past

Do you ever run into somebody from way, way back - and end up shocked that you really don't remember? I grew up and went to school in a small town where everyone literally knows everyone. I also have a very good memory. So I was surprised when, while at a store in the mall checking out today, the cashier asked me if my last name used to be Fiskari. I was like "yeah"...and he said "I was from Cook too". I studied him but still had no clue who he was. Finally he told me his name, and it started coming back to me. We made small talk a couple of minutes (I'm doing well, did you know X is in prison, blah blah) and then I left. Still wondering how I could forget anybody who went to the same school as me, seeing as how there were only 35-45 (give or take) people per class at the time. Granted, this guy has changed a LOT since then, but still. If I recall correctly, we were even friends at some point. Yet, I still could not remember. Am I really getting that old?! Ugh...