This happenedto us in 1980. We were on the M6 in an austin allegro, in the middle lane. A lorry with left hand drive pulled out as we were passing, hit the back third of the car and pushed us sideways up the M6, with our car side on to the front of the lorry. The driver put his brakes on immediatly he hit us and so we only got pushed his stopping distance. Can't see how the lorry driver wouldn't notice; our car was making a loud noise. Fortunately neither of us were hurt.
mel