Unexplained Absence

If a face-down creature loses its abilities, it can’t be turned face up with a disguise ability because it will no longer have a disguise ability (or a disguise cost) once face up.

If a face-down spell leaves the stack and goes to any zone other than the battlefield (if it was countered, for example), you must reveal it. Similarly, if a face-down permanent leaves the battlefield, you must reveal it. You must also reveal all face-down spells and permanents you control if you leave the game or the game ends.

To cloak a card, put it onto the battlefield face down. It becomes a 2/2 face-down creature card with ward 2 generic mana and no name, mana cost, or creature types. It’s colorless and has a mana value of 0. Other effects that apply to the permanent can still grant it any characteristics it doesn’t have or change the characteristics it does have.