Hello there!
I accidentally started minecraft_server.1.12.2.jar instead of my start.bat and as expected the whole world was corrupted.
There were no recent backups (i dont know if you guys plan on doing such a thing as long as mods for that exist) so everything is gone which is pretty sad :(
To make sure this does not happen again, is it already possible to move the vanilla server into a subdirectory?
Otherwise i would suggest that feature to prevent that from happening to anyone again :)