My brother's friend walked in on me naked

A few months back I just got off work and I decide to take a shower because I was going out with friends later. This was back when I had long hair, so I had to dry it. When I get out of shower I decided to not get dressed right away to just dry my hair naked in the bathroom (which I do often). My brother and his friends were home in his room. So I'm drying my hair and I'm about done when all of a sudden my brothers friend opens the door. I am completely naked. I slammed the door on his face I can hear my brother and his friends laughing. I'm completely mortified. Mind you that I've been in the shower, did not leave the bathroom at all, the door is closed, and the hair dryer is on, so it was pretty obvious that I was in the bathroom. My brothers friend did not knock, just busted right in. He said he was sorry, but I believe it was all a joke and I am so mad at my brother still about it. Anyone care to share similar stories?