UPS lost my package, T-Mobile wont do anything about it

It appears I am now dealing with this issue as well. I ordered an iPhone 14 Plus on 3/3. It made its way to my local UPS Facility by the morning of 3/7. The scan indicated that it was on the truck and Out For Delivery. Never came. Later that evening, some of the scans were removed and the status changed to On The Way while it was Processing at my local facility. Expected Delivery Date changed to 3/8. Never came. Delivery date changed to: The delivery date will be provided as soon as possible.

This morning I called T-Mobile. The rep told me that it's possible that UPS Quality Control pulled the package at the last minute. Perhaps it was damaged and they need a replacement. They told me contact UPS and wait for the shipment.

I called UPS. The rep told me that it was scheduled for delivery today (3/9) between 11am - 3pm. I told the rep that my tracking number no longer provides a delivery date and that it's stuck in processing at the UPS Facility. The woman assured me it would be delivered today, and told me to file a claim if it doesn't come.

It never came today.

@cr2023, did you have to provide a Serial number when you filed a claim? I'm looking at UPS's claim documentation, and it indicates they will close the claim automatically without one:
https://www.ups.com/us/en/support/file-a-claim/supporting-documents.page

Where do I get the serial number of the device I’ve never received?