I'm sorry that you have lost so many saves, it has happened to a few other people as well and it might be related to either a bug or clearing history in your browser (assuming you are using the web build).
The good news is we are working hard on making the next update, and that will hopefully fix this issue, but for now if you want to ensure your save persists you should play the downloaded version.
Thank you so much for playing and enjoying our game though :).
Sorry again that the game keeps losing save files.