Sudden Unintended Acceleration in 2010 CX-9

[DBS50]

A week ago Sunday I was driving my 2010 CX-9 (around 19K) on the interstate to pick up my son from a birthday party. I changed lanes, put my foot on the gas pedal to accelerate, and suddenly felt surge of acceleration. Tried to brake, and it slowed the car some, but the engine torque was considerable, it felt like trying to rein in a wild bronco. Realized that I was experiencing unintended acceleration. Made sure I was pushing down on brake and not gas pedal so I could rule that out. At that point, felt I had to move over to shoulder as fast as possible. Did so and began applying emergency brake (I know that was mistake now). It slowed car more but still wouldn't come to a stop. Finally, put car in neutral and that stopped the car.
Had car towed to nearest Mazda dealer and they kept it for almost a week but couldn't find anything wrong (no electronic record left) and couldn't replicate. Only thing they could think of was that my all-weather mat had slid forward and depressed gas pedal. I reported to NHTSA but so far haven't found anything reported online about similar problems with this make and model. So I picked car up yesterday, but I am still very concerned that this will happen again, God forbid with my children in the car or with my wife driving.
Can anyone think of other suggestions of what I might do?