It is very common, I often used to deliver replacement phones to people who had had their phones fall of their belt clip, or out of their pocket down the loo, when lowering said trousers to defecate. I did it myself, except that I did it from the 'kangaroo' pocket on the front of a sweatshirt, when I lifted it up to access the male frontal area when going for a pee.
Giok