On my Schlage locks, in the ZwaveJS2MQTT control panel, set lock codes show up as a bunch of asterisks (********) and codes not set are blank. You might be able to use this to do some checks in yoru script, but I dont know for sure if you can read this data.
An alternative is Keymaster
Keymaster does work, but it is a little clunky and rough around the edges. Install creates a ton of entities. I had issues with it and got rid of it, but others have been using it in their AirBnBs and homes for awhile. Might be worth a look.