I do everything I can to not introduce a new ball into the game but things do happen and balls dissappear or get wet or, or, or. Sometimes there is no option but to get a new ball. I seriously doubt it would ever happend at a national event. There are plenty of balls supplied and would be very unlikely to happen. It does tend to happend at high school games, especially ones where the field is up against houses or next to roads. More than a few foul balls into yards and ball supply becomes a problem.