正式绿卡被寄丢了.临时绿卡已经延期两次,九月份就到期,

1. the most important thing about your GC is not the card in your hand. the most important thing is you are in the computer system. in another way. what ever you lost your card or don't extend the stamp on your passport, you still are a permanent resident.

2. as long as you return before your I551 stamp expired, go ahead go to china.