1. Check the current status: First, if your mail has a tracking number, use USPS Tracking to check the status of your package if you fear it's been lost. 2. Complete a help request form ...
If USPS is not able to locate the missing mail (EAD Card), fill out the USCIS Non-Delivery of Card online form. You will need the receipt number. It means that USPS may have returned the EAD to USCIS.