Did you try using the Customs Form # for tracking at USPS.com?
I recently sent a package from US to UK via USPS Express Mail Intl.
The package had 2 #'s. An express mail label # and a # on the Customs Form.
Per the LABEL #, the package was delivered 2 days later in Colorado. HTG.
Per the Customs #, the package was turned over for Intl. Delivery, and I was then able to track it via Parcelforce by that same Customs #.
And it was finally delivered in UK. (Yet the Express Mail Label # STILL says delivered in CO)
FYI readers... USPS Intl packages are no longer trackable online thru USPS.
I tried to use the Customs # to track the package via USPS, but the system said there is no such a # yet... I was told by the lady in the post office I will not track the status until it is delivered, is that true?