You raise an interesting problem, and I don't recall ever hearing such a serious allegation against the TC Service Dept. before. You're saying that in this case, the gun was returned in worse condition then it was when it was sent in to them.
I'm sure that there's been minor damage done to guns by them before in the routine course of successfully fixing them.
But one question that should be answered in this case is why did the repair technician touch the gun at all if as he claims, the gun was not covered by their warranty due to obvious neglect?
I do understand that because the gun was neglected that they're not obligated to fix it under warranty. But they are still obligated to use reasonable care in handling your gun while they are trying to assess it's condition and attempt any repair, which it seems the repair technician didn't do.
But that's difficult to prove unless you took pictures of it's condition before it was sent in to them. Also, if the repair technician denies damaging it, it would look like you did it yourself after it was returned to you.
All I can suggest is to try not to let them get away with it.
I would call TC back again and talk to the service dept. manager and explain the damage that was done and the circumstances.
Maybe if you get adamant about how the technician mistreated your gun then he will tell you to send it back in or will have the company reimburse you somehow, for some fair amount of money like the low purchase price that you paid plus the wasted cost of shipping it to them that resulted in it being further damaged.
If you need to send the gun back in to them to make the claim, then maybe you should do that.
If the Service Dept. Manager doesn't give you any satisfaction, maybe you should explain the incident to customer service. If none of them offer any solution to resolve the matter, then I would ask them for the name and address of the company President and send him a letter of complaint. At least it will get passed on to the head of customer relations or another company officer.
My wife has written similar complaint letters and received personal responses and results, including personal phone calls from the corporate president of Pizza Hut.
And I once received a personal reply, a personalized knife and a full refund check from the president of Buck Knives, Chuck Buck.
So don't give up the fight if you really know that your right.
Now that doesn't mean that they owe you a brand new gun. But they just might go out of their way to satisfy you for the actual damage that the repair technician actually inflicted on your gun. Or make another extra effort to fix or rebuild it.
Like the saying goes "The squeeky wheel gets the grease."
There's not too much more to lose by trying.
Good luck.