Vehicles despawn on collision with any other object (tree stump, fence etc.). In this case I will describe three actors:

Driver)
Can drive for up to few minutes after collision then goes into state shown in video below (from 00:21 to 00:35) indefinitely only fix is to relog:
https://www.youtube.com/watch?v=xEQwEi9fBSE
After relog driver is spawned somewhere on the path made between collision and black screen shown in the video above.

Passenger)
After the collision everything hangs (as if network lag occured) and stays that way indefinitely. Only fix is to relog.
After relog passenger is spawned same as the driver.

Observer - person outside the vehicle)
After the collision vehicle dissapears.