Sometimes a message doesn't get sent for whatever reason (e.g. a crash or shutdown). I can't find the message in the Drafts maildir (/new, /tmp, or /cur). Surely mutt must save the message somewhere that doesn't get wiped in case of an unclean shutdown?
Where do drafts go when mutt crashes?
mutt;crash
If you were still editing the message, saving a backup copy is up to your editor. If you've actually saved the message but haven't sent it yet, it's stored in $TMPDIR (or /tmp by default), with a mutt- prefix. You can check the filename in your editor while you're writing the message; mutt will keep that same file around until you've finished working with that particular message. The Drafts maildir is for messages you've postponed indefinitely; it copies the temporary file to there until you recall it