What was intended to be a small patch today for Serious Sam 3: BFE turned out to be something incredibly vile ruining the day for many gamers. It turns out the update is deleting saves on levels 1, 2, 9 and 12. A Croteam member spoke up on the problem on the Steam forums owning it up to a mistake and promising a new patch will fix the problem tomorrow.
Bummers. Hopefully this little mishap is just a one time occurrence and everybody can continue playing the game normally tomorrow.