My first real crush was my freshman year of high school. I asked a friend to find out if she was interested (smooth), and she said, "no." Though he claims she said it nicer than that.
Two years later, he brought her up, and I had no idea what he was talking about. I was able to piece together a vague recollection, but I couldn't remember her face or her name or anything. I realized I was so hurt I completely blocked out any memory of her.
I'm still pretty freaked out by that.