Losing your green card can be concerning, but there are steps you can take to address the situation. Here's what you should do if you've lost your green card:

1. File Form I-90: Fill out Form I-90 online or on paper and submit it to USCIS. The form will ask for your personal information, the circumstances of the loss, and any relevant details. Be prepared to provide information about when and where you last had the green card.

2. Pay the Filing Fee: There is a fee associated with filing Form I-90. Make sure to include the appropriate payment along with your application. Fee waivers may be available under certain circumstances.

3. Gather Supporting Documents: You'll need to provide supporting documentation to prove your identity and eligibility for a replacement green card. This may include a copy of the lost green card (if available), a copy of your passport, photos, and any other required documents as listed on the Form I-90 instructions.

4. Follow USCIS Instructions: USCIS will provide instructions on where to send your application and supporting documents. Follow these instructions carefully to ensure that your application is processed correctly.

5. Check Application Status: After submitting your Form I-90, you can check the status of your application using USCIS's online case status tool. This will help you track the progress of your application and know when to expect your replacement green card.

6. Temporary Evidence of Status: While you wait for your replacement green card to be issued, you can request temporary evidence of your permanent resident status by scheduling an InfoPass appointment at your local USCIS field office.

7. Maintain Documentation: Once you receive your replacement green card, make sure to keep it in a safe place. You might also consider making copies of important documents and storing them separately to avoid future issues.