2010 LEXUS GS 350 Engine Problems

I WAS PULLING INTO A PARKING SPACE, DRIVING VERY VERY SLOWLY, ABOUT 1 OR 2 MPH, AND MY VEHICLE EXPERIENCED UNINTENDED ACCELERATION, BOLTING FORWARD VERY ABRUPTLY. I WAS ABLE TO STOP THE CAR BY APPLYING EXTREME PRESSURE ON THE BRAKE FOR A FEW SECONDS. THE DEALERSHIP REVIEWED THE CAR AND SAID THERE WAS NOTHING WRONG. THEY SUGGEST THAT I MIGHT HAVE STEPPED ON THE BRAKE AND ACCELERATOR AT THE SAME TIME, WHICH THEY DID TO REPLICATE THE EXPERIENCE. HOWEVER, NOW THAT I HAVE HAD OPPORTUNITY TO CONSIDER THAT, I DON'T THINK I COULD HAVE EFFECTIVELY PRESSED BOTH SIMULTANEOUSLY TO ACHIEVE THAT ABRUPT ACCELERATION. IF THAT WERE POSSIBLE, AND IT HAPPENS MOSTLY IN LEXUS AND TOYOTA, IS IT A DESIGN FLAW WHICH MIGHT ENABLE THAT? *TR