The note you've received from USPS means that a postage label has been printed for the item, but at the current time they do not have it registered in their system. I occasionally ship items, and I print postage labels at home through USPS - when you print the postage label you get a tracking number, which you obviously have. When I do a search on a tracking number I've just created it gives me the message you're receiving.
This could mean a few things:
It's still sitting at the vendor's in a box.
It never made it to the USPS facility - various reasons - 'borrowed' by USPS worker etc.

In my opinion you need to call the vendor and 'suggest' they send out a replacement, unless they have a good reason not to.