Sorry to hear about that. I know EXACTLY how you feel. (Well, not exactly since it wasn't my X)

Consider your self lucky that you were there. About 4 years ago, my wife's Accord, did the same thing, except she wasn't driving it at the time, it was parked in the garage and had been there for 2 days!!!!!

We found out that a relay was bad and shorted out, causing the plastic housing to melt and ignite. Luckly we were home and heard the tires explode . The fire department came with in a few minutes, but by the time they out it out, the car was totaled and we had about $80K in damages to the house .

Good luck and park it in the driveway