Glad you didn't have to bring this one in with the oil spray.
I'm going to be a jerk about this one. Not to OP, but to the mechanic. I'm not a lawyer, but do work a bit with them every day. To me, if the mechanic followed the manufacturer instructions, then it would be a warranty issue. But the statement "I don't follow the service instructions", to me, is the same as saying "I'm designing this repair method". I'd sue the guy even if an attorney wouldn't take it on contingency. Just to get the guy to say "yeah, I left out the Loctite because my method is good enough". It's not possible to convene a jury in the United States where at least one member doesn't know what Loctite is. Or what following the f&*&ng directions means.
I'm being a jerk because, from my understanding, this guy ignored the directions, installed the part wrong, and could have killed your family. The 20k hurts, but the alternative would be unforgivable. Guy should not be turning wrenches.
If a mechanic is going to deviate from the rules, they need to get the OK from the poor SOB that's going to be flying the aircraft, at a minimum.