1 of 3 Cell Phone trade ins lost

I mailed three iPhones in for a trade in to get new phones.  All three were dropped off at the same time and two of them have been processed and credits applied.  One of the phones (an iPhone 14 Pro) is showing as "not yet shipped" by the USPS.  It was taken directly by a Postal worker along with the two others that was verified received.  How do I check if Xfinity received my phone?  I started a missing mail investigation from USPS with no luck. I think Xfinity has my phone and has not processed it.

Please help!