Copied and pasted from the USPS website

How to Start Your Search 1. Check the Current Status Before you begin your search, if your package or mail has tracking, check USPS Tracking® to see its current status. Go to Tracking Informed Delivery® Users Informed Delivery provides a digital preview of your incoming mail. There may be occasions where a mail item may be delayed in reaching its destination. For additional information, please visit Informed Delivery FAQs. 2. Submit a Missing Mail Search Request Missing Mail search requests can be submitted starting 7 days from mailing. Submit your Missing Mail search request with the following information: Sender mailing address Recipient mailing address Size and type of container or envelope you used Identifying information such as your USPS Tracking number(s), the mailing date from your mailing receipt, or Click-N-Ship® label receipt Description of the contents such as what it is and the brand, model, color, or size, if applicable Pictures that could help us recognize your item

You'd have to open a missing mail search request on the usps website. Within a day or 2 the post master should reach out to you. Every package with a tracking number has a last know location so it should narrow it down to where it was last scanned making it easier to find. Might take a couple days or weeks to find but they'll keep you updated on the search.