Lazy post man is my call. Call the post office and ask them to look around for the package. If they dont have it, have them ask the driver. Sometimes they scan things before they're actually delivered/on the truck just to get it out of the way. You'll have to call early (right after opening) before the trucks head out.
Or, check your mailbox, around your front door, or if you have one around a back door....sometimes they'll just leave the package so they dont have to come back. Also check with neighbors, sometimes they'll leave it with them for the same reason.