20K is about the size of an empty Word 2003 document, so you
probably saved an empty document over your 60-page document. If
you have the "Always create backup copy" option turned on in Word
(Tools->Options->Save), then the old version should be in the
same folder as the current version but with a .wbk filename
extension. If you don't have the backup option turned on, then
the old version is probably gone.