That's already been demonstrated to be a side effect of a still-spinning rear wheel:

https://www.youtube.com/watch?v=Ak7xP8eghog

It should also be noted that "incident" occurred on a fast downhill section while Hesjedal wasn't pedaling so even if there were a motor it is exceedingly unlikely it would still be engaged at the time of the crash.

With a plausible physical explanation and no way to go back in time to check the bike for a motor, there's not much for the UCI to go after even if it felt the need to.