So sorry to hear this. I have dealt with a lot of these 3 letter delivery companies and UPS is easily the worst of them all. One time it took me 10 calls to get a box delivered from A to B, and not get doublecharged. They're unable to fulfill their very basic main purpose.
The insurance should cover it provided it was in a hardcase and you have photos before posting. Such a source of anxiety, I haven't shipped a bass in a number of years, always jump in the car.