It really sucks that happened to you and i don't envy your position. But i do hope you take this as a lesson for all EA titles and take my advice and back up your games manually after each session. It takes very little time and gives you a whole lot of peace of mind.
I do this particularly because it is an Early Access game, a fact you would have had to have seen on the store page. You agreed to buy into the game in its current state.

TL;DR: Sucks but its the nature of every single early access product on steam and everywhere else.
Early Access = Pay to test