You said there is a Gibson dealership near the "luthier" that did the repair. What if the dealership had a look at your guitar and documented for your insurance company what is wrong with the repair and what it would take to make it right. It also wouldn't hurt to have some photo's of similar repairs the dealership has done to show the insurance company how it should look. If they are anything like my old insurance company they will make a fuss about it, just stay on them until it is right. I wish you luck with this, it's sad to see someone messing up one of your instruments.