Removed from game

[Mulletus]

A couple newer cards have capabilities to return face up cards from out of the game back to either the library or graveyards. Are the only facedown cards that are out of the game your sideboard? Like once removed for any other reason they are all face up and public right?

[quicksilver]

Unless the card that removes them specifically says they are removed face down, such as Intet, the Dreamer.