Hey Lisa,
I've got the scanned delivery notification for my PO Box. Even 'supposedly' in the same building as the scanning is actually being done, sometimes I don't get the packages until two days after the notification. If t's 4 days after the notification of delivery and package still hasn't shown up then I'd start getting worried.
Be patient guys. My roommate is a mail carrier. The only way he's had any days off since Oct is to call off. They are being mandated to work 7 days a week. A few of those days are short 6 hour days but most are a full 9 hours and a few are 12 hour days.
I had just a small amount of seeds to send in so I sent them regular first class mail. It'll be interesting to see how fast they get there...