The only thing I've had come out of pockets inadvertently were sticking out to begin with, or that got dragged out when I was meaning to get something else - loose bills (money), gloves, cap, warmer, a wadded up windbreaker where the part that was sticking out caught the wind.... Anything could happen in a spill off the bike, but I think there would have to be something holding the pocket open in order for the phone to just bounce out on a bumpy road.