Thanks for your reports about the last hotfix messed with the save files. We just released a fix for this. We are sorry for all inconvenience this has caused.
If you lost your progress (weapons, skills, characters and maps) please contact us via the bugreport button in the main menu and attach a screenshot (of the prepare run screen with markers on what you had unlocked) or a list of things you had unlocked and want to gain back. We will then try to restore this progress on your save file and send it back to you. You can also contact us via discord if you want.
You can directly access the bugreport form to submit your save file with this link:
https://www.strivingforlight.com/bugreport/
Save files are located at: %appdata%\Roaming\Godot\app_userdata\StrivingForLight-Survival
Edit: We are already working on a backup system that will create a backup of your save file one time each day so that you can restore your progress for all kind of unhappy events.
We always try to adress bugs and issues as soon as possible and ask for your understanding for any inconvenience caused by our errors.