Glad everything wasn't as bad as it could have been and that you are safe! It could be the evap system as well. Have you checked the battery area?
This reminds me of a similar situation where I slowed because person ahead was making a right (I had my first car back then, a 2002 Accord) and a lady in a similar caliper car to a Cavalier comes SLAMMING into my rear end. Snapped my neck back good. I had the same expectations, rear end smashed to the frame. Walk out and there were only two little vertical lines on my bumper, the paint wasn't even chipped, from the ladies license plate. Her car was totalled--frame smashed in, radiator fluid dripping, hood flipped open, smoke everywhere.
2011 N55 135i | Wagner Tuning Highflow DP | AA Signature Exhaust | JB4 Stage 2 | LCI Tails | ER CP
2016 M3 | AWE Switchpath Diamond Black 102mm