that must be an OLD autosave copy.
maybe you created a new location for autosave by mistake in the scratch disk settings.
maybe you are looking in the old one, not the new one?
sometimes it helps to do a Spotlight search for "autosave"
you may find the newer one.
but the "Revert" function under the File menu should open the last autosave version, wherever it is.
otherwise auto save may have stopped working..
sometimes it does stop.
good luck,
nick