Just look in your log files. Here’s my log file with the keys scrubbed, which I discovered while hunting down an unrelated issue.
https://discourse.joplinapp.org/t/keep-original-notebook-on-...
https://discourse.joplinapp.org/t/keep-original-notebook-on-...
https://discourse.joplinapp.org/t/keep-original-notebook-on-...
I just checked my log.txt file and I can't find mention of my master password. Maybe it is fixed?
I’m reasonably happy using Obsidian now, despite it being closed source and not supporting anything but proprietary sync mechanisms. I have no had any data loss issues with it.