Quick update. It wasn't the 12V although sounds like they replaced it.
I haven't got the full diagnosis yet but they are replacing the HC battery and rear drive.
I'm sorry about my hypothetical "I wonder what would have happened if I wasn't parked" so you could make a snide remark, I know how an ICE would react to 90% of situations, I've only had 2 EV's and never heard of these situations so apologies for having NO CLUE what the car would have done in...
I was parked last night, about 10 minutes in the parking lot, about to go camping. I hear this crazy metallic crash noise followed by a hissing air decompressing sound. I go to the back of the car, see brown smoke spewing out the back. It smells like gunpowder. Head to the front of the car, now...