Could you tell us how the bike ran the last trip out? Any funny noises? Power ok? Overheat? When was the last oil change? Did the bike backfire on startup?
Find it hard to believe that the oil pump gears would simply break. If your engine backfired on startup, it is possible for the gear to fail (hopefully not due to a case idler gear/bushing failure). I can only imagine the gear exploding if something entered the inlet side of the pump. I hope nothing was dropped into the engine recently? Was the valve cover off recently? Oil change done? Grasping at straws here.
If the pump failed while driving, then everything Ian mentioned might have happened.
