They were able to recover the floor mat, and it was a rubber floor mat from an RX, not the ES. Its all just assumption...
So what are you saying, that the electronic throttle malfunctioned causing the vehicle to accelerate out of control, and the engine control computer malfunctioned not allowing the transmission to be put into neutral...at the same time. The chances of that happening have got to be incredibly, incredibly small. You're talking about two systems which work together, but are not dependent on each other to function.
Occam's razor, its far more likely that he just did not put the transmission into neutral. Training aside when your family is in the car and screaming and crying...sometimes people don't make the same choices in a crisis that they do in a more controlled situation.