My family used my car for a road trip and when they came back I noticed that my passenger side seat adjuster was broken and then this rolled out from underneath it the seat, I have no idea what it is tho.
That is the flexible driveshaft that goes between the seat motor and the seat adjuster. You may be able to reach under the seat and reinstall it.
I sometimes find water bottles or shoes stuffed under the front passenger seat causing a fault in the occupant detection system, in your case they only broke the power seat adjuster.