You were left in fetal position on the floor, because you knew no one was going to come back and finish you off or kill you, right ? and it was probably smartest to lay there until medical help arrived.
It is a whole different situation when you are fighting for your life, and there are cases where people do not even notice the pain because of the adrenaline rush.
But you are right that people have different pain thresholds, it is a medical fact; so anything is possible.