I got my car back today and just got back from looking at Toyota's assumption that a rubber floor mat designed by Toyota for the Prius was moved sufficiently such that it was able to contact the gas peddle, depress it and cause the acceleration which resulted in the left front brake bursting in flames.

1) It didn't happen because, well it couldn't. The mat is heavy and stiff enough (with all them little fingers on the underside to dig into the installed carpet) that we could not slide it forward. Besides the design of the mat fits around the foot rest which also blocks it movement.

2) To recreate what Toyota created, i.e., the mat over the gas peddle, as I recall the lower margin of the peddle, I moved the mat by picking it up and placing it on the peddle.

The peddle did not move. It was not depressed at all by the mat. Further, I pushed down on the peddle with the mat in the position shown by the Toyota photo, the mat dropped off the peddle.

I went even futher by placing the mat over the peddle. The peddle, was not depressed by the mat. Placing my foot on the mat/peddle, and then releasing the peddle with my foot, caused the peddle to return to its neutral position.

Finally, I tried all of the above with the engine on (as well, the emergency brake) and ran the test again. The engine failed to race with Toyota rubber mat on the peddle.

I had my wife depress the peddle/mat, and than release them. The accelerator returned to its neutral position.

Anyone owning a Prius with Prius rubber mats can (in fact, I urge you to) try these series of tests.