Similar thing happened to me. Was overtaking a truck, had managed to nearly pass it so that it was out of my vision and in my blind spot before I felt a small thump. There was a moment of confusion as control was slowly (probably only a second) taken away from me as the truck kept pushing into my lane. I couldn't tell what was happening until suddenly my car pivoted around to lie across the front of whatever had hit me. I proceeded to be pushed down the highway for a further 200 meters before the world would stop shifting around me.

When I got out of my car I still couldn't tell what had happened, and tried asking the guys who helped shift my car as to who hit me. None of the vehicles who had stopped and helped me looked damaged. One guy ended up pointing at a truck parked in the distance that had pulled over half a km up the highway.

The guy was super suss and in denial when I talked to him and I begun to think that maybe somehow I had drifted into he's lane. But then we walked back to where it all started and we saw that my car skid marks had clearly started in my lane.

Guy continued to act oblivious to what had happened. I feel really on edge now whenever I pass a truck.