statistically, pull out all of the stuff in the floorboard of the front seat, under the seat, and so on. Check the action mechanically and visually for anything that is binding, or too close to the surrounding action. Then check the action for proper voltage at test locations, several times, ideally with an o-scope or quality DMM. Attach scan tool and watch live data for the sensors/modules in question.
Does the acceleration happen, in park or on the road? Certain speed, cruise control working as designed? Does the pedal spring back at all times - no matter the angle of your foot pushing it? Are the drivers shoes cleated, high heel, encrusted in material, etc.
If none of this fixes things, Toyota usually then digs into the accelerator assembly, and replaces those that were suspect...I am not up on the other makers who had issues, other than the vendor Toyota used, also made similar assemblies for other car makers.
Now all that being said, the investigation turned up only a very few actual documented cases, like single digits of the millions of cars sold during that time. Troubleshooting, codes and failures could not be duplicated. There were quite a few, floor mats not affixed, pedal being trapped by heel cleats and so on.
If your co-worker is worried about the risk, and chooses to keep the car, please educate and show her/him how to turn things off, place the trans in neutral, etc in hoping to mitigate the risk.
Contact Toyota directly, at least at the region or zone. All else fails, attorney familiar with the investigation and vehicle systems.