Document didn\'t save

yesterday I created a document. and shared it.the guy with whom I shared did some changes and i received it today mornig. then i did some changes again and saved the document(I did press the save button, and it showed document saved)
but after an hour when I asked the oter person to see the changes he said i can't see any changes except an extra No is added. That "No" is the starting of a line i wrote. But thats the only chage it retained. Nothing else. All other chages is lost, and nothing in history too. The strange thing is I saved the document, but in history it is showing the last save 16 hours ago , i.e yesteday evening. but then how the extra "No" came? I am confused any help!!!
sumanpau