Lesson learned: when you move update your address on every single website you have an account on. Also, you should do the USPS change of address thing before you move. I know I am not telling you anything you haven't figured out already, I know it sucks.
Don't know what to say really. If USPS said it was delivered it probably was. If someone else picked it up and wants to lie about it, not much you can do.
'11 BMW E92 ///M3 - ZCP and DCT
'13 Toyota Tundra - 4x4 Platinum CrewMax, 5.7l iForce V8