Assurant return damaged device package Empty!!

Going through a similar issue right now. Dropped off my phone at a UPS Store 6 days ago and watched the guy put the package into the USPS bin. Got an email from Assurant yesterday saying they haven't received the phone yet and when I called them they said they have no information of it being sent. Unfortunately, because it was a UPS Store and it was a USPS label they were unable to give  me a receipt/tracking number, but I've used this same UPS Store for years and have never had a problem with them, and again - I saw him drop the package into the USPS bin immediately after I handed it to him. I've been a T-Mobile customer since 2004, but this latest experience with Assurant (it was a nightmare just trying to get my claim processed) really has me looking at finally switching my service to someone else.