Well, precisely. And that's why the T&C specifically spell out that no, you get nothing. You lose! Good day, sir! Well, it's sort of a win because your idea went into the game, but it's no longer your idea; it's theirs. Hence, if you want any credit for your idea, keep it hush-hush and arrange with the developers privately. Personally, I love the idea of my input being part of a creative work, but I wouldn't ask for money in return. Heck, in this case, I paid $5000 for the privilege of possibly having some of my ideas used in the game.
Hey, there's an idea for a T&C modification. If you post a gameplay idea on the forums, and it gets used, you owe QFI $5000. That would keep people honest! "Oh, no, that idea in the game is NOTHING like what I suggested! I have no claim to it whatsoever!" Now there's a way to reach your stretch goals!