That's absolutely terrifying...that level of incompetence is worse than being a little lazy or not being familiar with a bike - that is "I'm trying to kill you" levels of sabotage IMO.
Then again, I had a "mechanic" leave the entire lower triple not even finger tight on my old race bike. After a stop to stop tank slapper (leaving me with no front brakes till I pumped them back up) that I managed to ride out pulled out of the race and into the pits to eventually find the bolts ready to fall out after starting to go through the front end bolt by bolt to see what was going on.
That was the last time anyone touched one of my bikes without me hovering over them and often going behind them double checking everything, even for super minor stuff. Even Shawn gets the hover treatment but he's about the only person I will trust to do things I can't specifically check once he's done
I'm far from a great mechanic, but I want to know what's going on with my bike!