I worked at the local Post Office for five years. But with Piority, I have noted that the date the postage was placed on the package is not necessary the date it was shipped, it is just the date the postage was printed. I have noticed 2 to 3 days difference before the package arrived at the Post Office. If there is a delivery comfirmation, the USPS scans the package everytime it is handled. I have no idea why it has been at your local Post Office for several days, I would call them with the information you have. We had strict orders to see that Prioity was delivered quickly.
If this was something you purchased using PayPal, your first notice was probably sent by PayPal. The Post Office does not send e-mails to individuals. Once you have the confirmation Number you can go to track & confirm and request updated information via e-mail, however this information is usually not updated in minutes/hours sometimes just overnight. There have been times when I received the package before the updates, but I have a P.O. Box and mail is put up between 7:30 a.m. and 8:30 a.m. At our Post Office Parcels are put up first. We were small and P.O.B's only, so we frequently called customers who were waiting for packages to let them know it had arrived.
I have never had a problem with Priority, especially with delivery confirmation.