I left my original papers ( admittion latter And jw02) in the embassy :-o

After I submitted all the paperwork to the embassy. I got my passport only but they didn't return the original papers(admittion notice &jw02) , and I did ask them back because I didn't know.I was supposed to keep them! What Can I do? Is it that some embassy keep the original papers? Don't I need them in China for vissa extentions after I enter The country? As I got 30days vissa from my date of entry. What can I do to get the original papers backs or its not that. Important? :-(