I ran in for a quick little trip to my local store, and while wandering in one of the aisles when I heard a friend, "Hello." I barely had time to look up and say hi back before he was on his way down the aisle. It didn't hit me until a few seconds later that he was just some random guy talking to me...and he was really cute!
I managed to see him again on my way out. I got in the same line. When he finished check out, he simply looked up, smiled, and went on his way.