Thanks so much for the praise and for taking the time to write such a thoughtful comment. It really made my day. No it's not long winded at all, I genuinely enjoy reading everyone's stories and feedback, and that is a huge part of what keeps me motivated to keep developing the game.
About the missing save file, do you know if you recently cleared your browser cache, browsing history or switched browsers (E.g. Chrome to Firefox/Safari)? Serenitrove stores its save data directly in the browser, so clearing the cache would remove the save as well. Another possibility is if you switched from the browser version to the offline downloaded version. In that case the save needs to be exported from the itch.io browser version and then imported into the offline copy.
As for secret codes or "Konami code" input, I am afraid there is nothing like that implemented in Serenitrove. I do use internal debug tools during development to unlock resources or test features, but those are removed from all official releases.
That said, if your save is truly gone and you REALLY don't want to replay everything from scratch, I am more than happy to help. If you can roughly remember your progress or what you had unlocked, I can try to craft a replacement save file for you.
Thank you again for the incredibly kind words and encouragement!