Well, the most logical option will be to copy your entire save folder from the previous release into the new one. Just as I recommend doing with each update.
Moreover, how did you lose it?
Viewing post in Yorna: Monster Girl's Secret comments
This sounds like a serious issue. Do you use Itch client to launch Yorna and synch with new updates? If so, you may want to consider contacting support. This is the first time a player got such a problem and it may be tied to the launcher.
Since the last public update was the same as always, I don't have any ideas about the cause.