Depending on how high the aircraft might have been, how fast it was flying and its direction of travel the ice could have come off the airplane a long way from where it struck the car. It would take a while for a piece of ice to fall 30 or 40 thousand feet and it would travel quite a distance if it started out at say 200 mph.
Commercial aircraft cruise at a little over 500mph. Even a longer way that the ice can go.