If an applicant has missed their green card interview, there are generally two options for rescheduling.
The first option is to reach out to U.S. Citizenship and Immigration Services (USCIS) Contact Center by phone. The caller should be ready with their alien registration number, and Form I-485 (adjustment of status application) receipt number. When the applicant has spoken to an agent at USCIS, they should ask explicitly to be escalated to a Tier 2 officer.
The second option is to write a letter. When writing the letter, the applicant will typically include all their contact information, as well as their A-number (alien registration number) and the receipt number for the adjustment of status application (Form I-485). If the applicant has proof that they filed a Change of Address (Form AR-11) at any point, they should also include a copy of the confirmation with their letter. A copy of the I-797 receipt notice for the Form I-485 should also be included. Typically the letter is not long — it should clearly explain why the interview was missed, and any pertinent information explaining the situation.
The applicant can keep a copy of the letter for their own records, and it’s generally a good idea to maintain tracking on the letter so they know when it has been received.