What if the green card application was denied?

Contact USCIS as soon as possible. Ask them to make a note that it has been lost. Make a police report as soon as possible. To help you in future appointments etc.

Find any USCIS letters that have been sent. Note your Alien number and reference ID.s.

The newest letter is the most important because it proves you are legal.

You may need a stamp in your passport so contact your local office.