Someone please explain this to me

[jianantonic]

So, say you're busy or occupied or for whatever reason can't get up, and you find yourself struck with the urgent sense that you must go to the bathroom immediately. Only, you can't. So you tough it out, miraculously not soiling yourself, and when you're finally free to get up and use the loo...you don't have to anymore. Um...where did it go? Just curious.