Oh no, that sucks :( Hopefully, it's not all lost... In the future, try putting all of your game files in a git repository, do regular commits and push it to github or smth. This saved my a** a lot of times!
I'm unfamiliar with Unity, while this really sucks, use it as a learning experience. Even for small projects like game jams, you should always use a file saving service like git to regularly make backups of projects. It's saved me a few times, and it hopefully can for you too!
Jams are to learn somethign new. And this mistake everyone of us did sometimes in their career. What you have to do now, is learn how to use some kind of git with unity. It's a must have if you work together with others and it is a nice help if you work alone, because you can step back to an older version of your project if you made a mistake.
