My goodness!
I would not stop communication with UPS...I would send a communication to the CEO outlining your experience.... maybe with a cc to the supervisor in charge of shipping or tracking.
They have to know where it is....everything they handle is barcoded and scanned on arrival and departure from wherever it lands.
Do you know where it "went missing"? Someone has the tracking number and if you can get it and plug it into the UPS tracking site you will get a clear log of it's handling.
Hope you get it back soon!