Lesson to be learned here, don't let anyone touch your bike but you or someone you really trust , I'm not saying they defo did it, but I took an XT600E in to a garage for an MOT and they suddenly announced that the front disc was warped, I would've noticed the "pulsing" of the brake had that been the case.
Also, when I tried to change the front sprocket, they had done it up so tightly it had to be cut off.
I use an MOT-only garage where I can wait in a viewing bay now.
A biker friend who knew the garage said it was not unkown of them to put a stout screwdriver or similar and twist to get more work.
So your stripped thread might've been that sort of mechanic.
Do it yourself and know it's done properly.