Is there any way someone in your building could have overheard you talking about getting your phone? Like a neighbor overheard your conversation through the walls, or door? I just think it is so coincidental that some one was standing in the lobby at exactly the moment when UPS delivered the package! What are the odds of that?!?
My other theory is the UPS guy never actually delivered the package
I think UPS should have had to do an insurance payout, even though it wouldn't help you with getting a new phone, only with paying the EIP (assuming you have an EIP).
T-Mobile should have sent you out another phone right away..I don't think you should have the wait another 4 weeks for a replacement. I hope to h*ll they aren't sending you a refurbished phone!!!