Remarkable: Great use of sound!
Needs Improvement: I agree with the other suggestions - some interactions beforehand might connect the player more to the experience.
Successful: As someone else mentioned, I think having items disappear while I'm not looking at them is actually spookier than it happening while I'm looking at them. Either way, it's a terrifying effect, especially coupled with the music.
General: Lots of great suggestions from others on where you could take this, but as a prototype I think it's very effective.