UPDATE (1/22):
They told us a few days ago that the floorboards were damp. It turns out that there was a leak in the air conditioner (I believe it was a hose) which caused some wiring to get wet and corrode which ultimately led to the car dying in the middle of the road.

My guess is that this was a progressive problem that was worse over the summer when the a/c was actually being used and just manifested itself now as the wires continued to corrode.

They say everything is fixed and ready for pick-up tomorrow morning.

We'll be watching things very carefully to make sure this hasn't caused any more damage.