What rule is that, getting pushed out of sand?

As per many sports car series

really, never seen it

it's true, they use tractors or things like that with ropes though IRL

It shouldn't be too large a concern, because chances are by the time the caution comes out and the RB4 finally gets there, you would have lost quite a large amount of time.

F1 doesn't have it because the cars use remote starting, and once they loose the ignition they're done.