HP Death Hallows Hidden Room Question?

My theory is that the room didn't show him the other stuff. Voldemort needed a place - that no one else knew about - where he could hide the diadem, and the room gave him what he required - at least in appearance, if not in fact. Remember that Fred and George once needed to hide from Filch and the room became a broom cupboard. It didn't become the entire storage warehouse for them to hide in.