The game crashed last night and uninstalled itself. I’ve lost all of my game worlds and had to re-install the game.
The game can not uninstall itself.
If you are sure that you did not do anything to uninstall it, please make sure that you have no virus, worm, malware or any fourth party programm installed.
No viruses/malware. I think Steam may have caused the issue.
The game itself cannot uninstall itself. I’d suggest visiting the steam support page and having this discussion with them but i’d also suggest running an anti-virus/malware program to see if that doesn’t resolve your issue. Sorry i couldn’t be more helpful @IzakJackson
Maybe you run the game from its folder? There is an uninstaller there with the same icon of the game, maybe you confused the two and run the wrong one?
Even if the game would have “uninstalled itself”, the save files should still be there.
That’s how my folder looked after uninstalling;
and the save files stayed there after reinstalling the game (just tested it).
In order for the saves to be lost the whole Stonehearth folder would need to be deleted, what steam doesn’t do. So I’d suspect malware, too, or alternativly a really bad cleaning program (something like CCleaner just in worst) or a defragmentation program or a corrupted harddrive…
Uhm… no? (Or I’m just blind)
All the files were wiped 
I launched the game through Steam.