You can check the MIRA coalition or check for pro bono attorneys with the bar. Also, with every paper filed you should have received a receipt. You can send copies of those to USCIS attached with a letter. Each receipt should have a number and address. In the meantime, you should also do a FOIA request to check if they really lost your file.
Specialist_Run_8238 t1_j9tj0sj wrote
Reply to Trying to get Grandma out of Ukraine, who do I turn to? by BF1shY
You can check the MIRA coalition or check for pro bono attorneys with the bar. Also, with every paper filed you should have received a receipt. You can send copies of those to USCIS attached with a letter. Each receipt should have a number and address. In the meantime, you should also do a FOIA request to check if they really lost your file.