There's no doubt about it i'm afraid. If you scan it for fault codes it may point towards the pedal and the sensor but it will be the ecu. Are the wires frayed? If so it could have been happening slowly and when they removed the sensor without disconnecting the battery, they have shorted the wires and fried the ecu. At the end of the day the car drove on and had to be pushed off the ramp so the are liable and I would be looking for a replacement car while it is off the road!
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