Look, you are being silly now, the chances of that happening in the first place are probably far less than a pedestrian stepping out in front of a car [clue, there are more pedestrians], add to that a helmet is going to be next to useless if hit by a vehicle.
My perfect bubble as you call it, well now as it has become personal, I have cycled in the region of a quarter of a million miles, raced, toured and ridden in some of the busiest cities. In all that time I have has quite a few "offs" as you might imagine. I have not once been hit by another vehicle and only on one occasion have I hit my head, this on spilled diesel where I considered it more prudent to save my bike rather than me. Either I am the luckiest man on earth or the most skilful, of course I am neither.