Here is what happens. When you open a document from email, it gets saved and opened from a temp directory in your temp user files. You can see a similar action if you download a large file in I.E., you will see it download, but to the temp files folder, then you will see it copy the file from there to where you wanted to save it. If you click SAVE directly without doing a SAVE AS, it saves it in that temp file. If you first Downloaded the file, without just double-clicking to open it, it will be in the place you downloaded it. If you just opened it without first saving it to the hard-drive, it will be in the temp files, which can get deleted, for example if you clear temp files in your web browser.
You can do a search for the document, and make sure you select to search hidden and system files, see if it finds it. If not, the edits you made may be gone.
You can try a file restore program like Recuva, they may find it in the temp folder if it was deleted.