That's horrible.
Your quilt is beautiful.
Have you tried escalating your issue with UPS to talk to a supervisor or manager? Keep calling back until you have talked to everyone they will connect you with.
I am not sure what else they can do. I did have a package go missing once and they told me it had been delivered but they couldn't say where. I kept calling and being a nuisance and low and behold the package arrived within a few days. They never could tell me where it had been or how they "got it back."
I hope this works out for you.