[Idiotekque]

No worries. Any form of USPS international shipping (even First Class) provides a DC number though. You can find it on your copy of the customs form. DC numbers prove you sent it the same as a tracking number will, but they won't have the frequent tracking updates that a tracking number will have; they'll likely just show when you gave it to the post office, when it was sent to the sorting facility, and when it arrived.

I think they make it difficult on purpose, in any case.