There is a known issue where, if the player fires up a new game from main menu after he came from an older game where he had discovered uniques already; that these uniques would not be loaded into his newly created game. This means directly making a new game after having played a previous one, without exiting the game.
This could for example happen if the person plays a singleplayer game and has found uniques in that game, a friend comes online and you start up a new multiplayer game immediately - thats when the uniques that have already be found before will be missing.
If you exit the game, then start it up again & make a new game, the uniques should be available again. This issue should be fixed in the upcoming major patch.
