the same happened to me as well ... hope the doucment mailed is FP rather than greencard as i still have to file I-485 for my wife and i don;t want to get it approved before that. But when i called the uscis customer service she said your green card is approved . hope that's no true.
There are all the status update i got since my FP 05/11,
Before that i got the FP was received reviewed and then these,
1) The last processing action taken on your case
Receipt Number: SRC04097xxxx
Application Type: I485 , APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS
Current Status: Notice returned as undeliverable.
2) Receipt Number: SRC04097xxxx
Application Type: I485 , APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS
Current Status: Document mailed to applicant.
Also to note i used the FP notice reciced by my lawer instead of the one that mailed to me as it went to my old addresss.
please let me know if you had any situation for you , btw i did my FP in charlotte . where did u do ?