Because he knew he had nothing to show so he made up some lie.. I mean seriously, who works on something for that long and then it all just gets erased? I have never had that happen where EVERYTHING got erased.. I mean why would he even be upset about it? I'm sure it wouldn't be too hard to remake if he made it once before.
If you didn't make backups or save, then I laugh at you, because by now you should know to save stuff and back it up, especially important things like that.
But anyone can get on here, show a half done "crappily put together" tileset, brag for posts and posts about how great his stuff is coming, and then say "oh no it got wiped! i'm angry!"
