My friends and I saw an internet rumour that when pedestrians are hit by fast cars there feet rapidly shrink which is why the shoes are often lost and could not find a definitive answer and opinion was divided. Two of the people present had also heard this before so we could not dismiss it as a one off. As an addition does this also apply to the driver?
I don't think that's possible. A person I know was hit by a car in summer and she told me a lot of things but nothing about losing her shoes.
Shock does drain the extremities from blood, but I suppose usually that will just make the feet pale and cool but not much smaller. Maybe if someone has swollen feet?
Although... on second thought, those shoes you slip into and out of without fastening anything - they might require only a very small change in volume to fall off...