Modders don't look for everything. Besides Skyrim CS is not out yet. I think.
Just a few weeks ago I found something in Fallout 3 files no one had reported before: a test minigame I suppose, probably an Oblivion leftover, for a small fantasy setup. It was entirely in text notes and just called "the game".
Quoting one part of this "game":
When you draw your sword, Grelok lowers his great horned head and bellows laughter in your face. You grit your teeth and swing a mighty two-handed blow, the magical blade ringing clearly, even amid the tumult of throaty cackling. You swing the sword so fiercely, it escapes your grip and hurtles into the open maw of the monstrosity, lost from sight in the arid darkness of Grelok's throat. You step back as Grelok jerks his mouth shut and stands upright. He is still for a moment, then starts clawing at his neck. Muffled, a ringing can be heard as if from a great distance.
Suddenly, Grelok's chest bursts in a fount of viscous, green blood. The Ringing can be heard clearly now, and as thick lifeblood oozes around the protruding tip of the magic sword, the stormclouds swirling the peak are already clearing. Grelok is defeated!
THE END
(Thanks for playing!)
I also lately found new unused dialogues for Fallout 3, being the first one to observe them. They involved the game's main villain, President Eden, taking part in person in a mid-game battle.
There are some things modders will never find, or find only find after several years.