oh so usually when you download something off the internet it goes to your downloads folder right? that folder is nestled inside a bunch of others that sit inside your general user folder. since devices like these usually have multiple users they separate all your stuff (including your downloads haha) into that general user folder is marked with your name to seperate you from other users (even if the computer doesn't have any other lol). so its pretty easy for them to go up the chain since the game is saved in there and read the file name and then BAM! they have your name :)

Tbh I only figured it out cos they had my name but it wasn't capitalised and this account doesn't have my name AT ALL!!   So after some very real fears that I'd been hacked ;( I remembered my folder was the only thing with my name on my laptop AND it didn't have it capitalised lol