Same thing happened to me once when I was about 12 or 13, only one step worse. I was spending the night at a friends house. Pissed on his floor! I wanted to crawl in a hole and die. I could even look at his parents. I was never invited to sleep over there again.
At first I wanted to hide it and quickly realized that it was impossible considering that I didn't have a change of clothes, there was a huge wet spot on the floor and my sleeping bag was dripping wet. By the size of the wet spot, you would have thought I had been saving it for weeks!