changes that you made, then you probably had a bad internet connection or something and the changes weren't saved. If you are talking about accidentally deleting the file, check your trash. If you are talking about accidentally deleting a bunch of text in the file and then it auto saving, do the revision thing everyone is talking about. You should be able to go back to a recent revision and get the deleted stuff back.

It is worth learning. It works way better for this type of issue than MS Office.