Usually, when your package has been marked as delivered but not there, it will show up in a day or two. Generally speaking, parcels sent with tracked services rarely go missing to the point where they cannot be found.
Please contact your local post office to see if they can locate the package. They are likely to have the best solution for you. If not, please submit a tracking inquiry here. Unfortunately, we do not have any control over the package once it leaves our warehouse.
Please let us know if USPS cannot provide a solution or cannot locate the package through the request submitted through the website. We will always try and work with our customers to provide a solution if USPS/UPS doesn't!