No, I also think it is the will paper , It cannot be a Key because if the water falls on the Key it should not be a problem , it has to be papers or some kind of object which might get faulty or spoiled because of water .
such a big paper in such a small locket..plz yaar its shown dat it was under d cradle...in 1 of d episode...use ur brains dear...it may be a microphone or a camera...2 keep a check on d family...