[Chi]

You mean when? Because I think by the feeling of pain in your butt you know where it is. xD;
Um, well bugs like to go wherever they please, so maybe he crawled up your shorts when you were standing or sitting down and when you moved he stung you?
Or maybe when you were sleeping, a bee decided to be a jerk to you and just sting you in your sleep?

Funny story just happened, I found a bug in my room a week ago on my leg and I killed it, I just now thought I saw a bug on my leg and smacked it, when I washed my hand, it was fuzz. :D