If the pedal was really stuck, like by a floor mat, the black box wouldn't tell you much. It probably didn't even save any data since there was no crash.
You CAN turn off a push button while driving. In fact, you can to it two ways in the kia: by holding it down for 2 seconds, or just by stabbing the button 3 times in less than 3 seconds, as you'd do in a panic.
The real question: why are the driver, mechanic husband, 911 operator, and the police all too stupid to tell her to do that, put in in neutral, lift the pedal with her toe, or just stand on the brakes. The fact that speeds varied from 80 to 120 demonstrate she was under control.
Originally Posted by http://www.kiamanuals.org/kia-590.html
You are able to turn off the engine (START/RUN) or vehicle power (ON), only when the vehicle is not in motion. In an emergency situation while the vehicle is in motion, you are able to turn the engine off and to the ACC position by pressing the ENGINE START/STOP button for more than 2 seconds or 3 times successively within 3 seconds. If the vehicle is still moving, you can restart the engine without depressing the brake pedal by pressing the ENGINE START/STOP button with the shift lever in the N (Neutral) position.