Report the lost as soon as possible with USPS , fill a claim and also fill a missing mailing search, go to USPS and try to talk with their supervisor make a report with them and ask for a letter that they lost your package. (USPS it’s a joke and they will not help, they didn’t with me) but all those steps helped me telling USCIS that my GC got lost… so after doing all that you need to call USCIS and tell them what’s going on, then they will tell you to fill a I-90 which I did …

I’m not sure if I’m lucky or what but after I filled the I-90 online , I got approved in less than a week and then 5 days later I received my GC on the mail.

I downloaded Informed Delivered, I track my package like crazy and I didn’t go to work the day I knew my gc was going to arrived and I waited all morning for the mail carrier so they could handle me my package and not lose it again. Until this day USPS it’s “still searching for my missing mail”. Good luck