WAIT a second! This means that Bombadil HAS to be a Maiar, since he didn't disapear, and he was NOT an Elf! Haha! Mystery solved if this statement is true!Grond said:Gandalf explains to Frodo while they're in Rivendell that the Ring actually takes the wearer into the world of spirits. He tells Frodo that is the reason he seems to disappear but in fact, is simply in another plane, the spiritual one. That plane is where the Wraiths features are visible and where the Elves' true spirits are seen as well. Remember how Glorfindel was described at the Fords as being a bright light. Frodo could see both the Wraiths and the true and bright spirit of Glorfindel at the Fords.
It doesn't make the elves or Sauron invisible as they already live in both worlds unlike Man and Hobbits.