It seems like you're stuck without any further answers ATM. Not until the UPS inspection is completed anyway.
Once that's done, go from there. Since the original packaging wasn't used, I would think UPS would deny any liability in the situation, and put it back on the seller.

From that point, it would have to be handled through eBay, and their track record isn't the best from other posts in the forum.
That's why I was wondering if you would be inclined to repair it yourself. It might not look pretty, but would allow you to use it, and avoid the cost of a new case.
Hopefully, UPS would accept responsibility, but the packaging I think is going to really cause a problem.
Sorry things haven't yet been solved. I'll keep my fingers crossed.
Good luck.