The delivery confirmation that the U.S. Postal Service offers is a good investment, but there are some misconceptions. First of all, is is not, and rarely operates like a tracking service. If it were to, the package's bar code would have to be scanned at every juncture of the journey, and that rarely seems to happen. Often times, I get a request for a tracking number, and provide the delivery confirmation number. The buyer, when entering this number into the USPS web site, gets the message that "there is no record of the item", or "USPS was notified electronically to expect your package for shipping". The package may be en route, but because of a lack of technology or effort by the post office carriers, employees or substations, it may not have been scanned yet. Many times it is scanned and confirmed as delivered the moment it reaches your door, which fulfills its role for confirming delivery, but but provides no "tracking."
So, buyers, be patient. A USPS delivery confirmation number will be useless to you until the item should have arrived.