The parts diagram he showed you doesn't have the parts related to the reclining function! Here's the one that shows you pertinent information. Not that a parts diagram really helps, but it appears now the cable is gone its a direct drive so it shouldn't fail really at all.

So my first thought is its the buttons or the control module have the problem. Solution: Jump them and see what happens. The control module is under the seat and connector B goes to the backrest motor. I think if you put a source between pins 1 and 2 the backrest should move. If it moves down, switch polarity. What's that you say, you don't have a power source right there? You're in luck connector A has one, and has it all the time! I really hope you have aligator clip wires, but its just slightly more difficult if you don't. Anyway, ignition OFF, hook up a wire from pin 2 on connector B to a ground. Then run a wire from connector A-1 to B-1 and the seat should move up. If not switch the ground and power on B to make sure it goes down (and that will assure you that it should have gone up). Down but not up leads me to believe the motor is worn enough that it doesn't have the power to come up. Next step would be to replace it (junkyard..)

If it works as it should, first make sure the buttons are working properly. Not really sure how to do this without taking it apart. Lets cross this bridge later. Same with diagnosing the control module (this might be easier just by swapping passenger seat with drivers seat module).
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If you're not driving it "like its stolen," are you really driving?