I used to think mashing was just mashing and it didn't really matter how you did it, but then a guy at my LGS showed me the same thing with my deck. He fanned the cards out and I could literally see the same chunk of lands and spells staying clumped together no matter how many times I did it. Now I split the deck into six or seven piles first and then mash those together, and my games have been way less flooded or screwed.

Oh man, that is brutal. My buddy Pete had almost the same thing happen, except it was his roommate tripping over the cord while Pete was saving after a huge skull cavern run. He lost like 60 hours and just sat in silence for a whole evening, wouldn't even talk about it. Turns out he never had cloud saves on either, and now he checks that setting on every single game he owns like it's a religion. I keep mine on now mostly because of his horror story, plus the cat thing feels way too possible in my house.