There have been a lot of theories online but they all seem as failures mostly. After watchin some scenes of the game I got to think that Riku carryed the blindfold becouse otherwise he would release Ansem. that's why the King is suprised to see Ansem in the forest scene, becouse he was in the body of riku. You can see it pretty clearly after playing trough the Re: Chains of Memories game, KH2 and watching the revealed scenes on youtube or KHinsider. Not noticing this would be like not noticing a fat kid in a dark room with a neon sign above his head that would say I'm here(shhhh...):31: