Where are the save files located
On windows it should be somewhere here: %USERPROFILE%\AppData\LocalLow\YYZStudio\Siegeturtle\File0.st
You can send it to me at havendockyyz@gmail.com, and I can take a look at what's wrong and if possible I will push out a fix on the game side, but if that is not possible, I will send you the savefile back and also refund you some extra skill points for lost time.
For a future improvement I will add more autosaves (e.g. 1 hour interval) so there is a further fallback in case of mishaps, as I imagine your autosaves only go back a few minutes.