After the immaculate reception the raiders cheated a forward fumble and recovered in the end zone for a touch down. That play became known as the holy roller play or something similar. I believe this is to keep teams from doing something similar to gain a touch down such as reaching out and breaking the plane of the goal line and losing control of the ball. It was a while ago that I read about the logic behind it and that is the best I can recall at this point, hope it helps.