@dsstrainer Thanks for sharing your find. I just tested it and it works fine, but only if the file is created (by touch in your example) when ES is already running. ES seems to delete the file at start up, because it's actually meant for ES' restart option, as I understand it.
Thus, to use it as an everyday fail-safe in case ES crashes you'd have to find a way to create it automatically after ES has already started (edit: and to manually delete it if you want to shut down ES for good).
Just an addition to your advice, since you don't need it yourself anymore. :)