Try the Auto saves.
Try the Save Copy as... Location ( if you did that occasionally/regulalrly as part of good practice.)
If not...start doing that Next time.
There's an option under the Pref's/Autosave tab for number of versions ... I've seen a couple people note that once they'd hit the number they'd set, it stopped saving rather than deleting an older one. I haven't actually tried to see what this does myself, but ... perhaps that's what happened.
At any rate, Shooternz's suggestion to Save As ... every so often is wise. Very, very wise.
Note : "Save Copy as"...Not "Save As".
Its easier to create and manage incremental versions with Save Copy As".
I just append "BACKUP 1, "BACKUP 2", Etc as I continue....
Creation date is then key to this.