USPS lost my trade in phone needed for a rebate

@RMani im going through this exact situation right now.  I mailed 2 phones (separately) each worth $830 in credits.  Mailed them on Nov 18th and one arrived on Nov 30th after sitting "in transit" for several days. The other is STILL listed as 'In Transit' since November 25th. Opened a case with USPS 4 days ago and have t heard anything back other than they are looking into it.  
 

Contacted T-Mibile with the IEMI of the two phones (since neither had arrived yet) and they said:

“I appreciate you contacting USPS to inquire about the trade in devices. 

As long as you mailed the devices before the grace period ends and we have received them, you can be assured that you'll receive the trade in credits for the phones.

I have submitted the handset escalation. Please allow up to 5 business days for an update on this escalation. 

No need to contact us back. You'll be receiving an email update about this from our Handset Research Team. 

I'll make sure to monitor this as well.

”

That was nearly five days ago and I’ve heard nothing since, even though one of the phones was supposedly delivered.

Mine have to be in by Dec 12th and now it’s already almost December 4th  

 I used their label, so they should honor the credit and they should be dealing with USPS to resolve this. 🙁