I have a question that has been bugging me since I first read the Silmarillion. A silly question perhaps, but it has bothered me nonetheless.
In the story of Beren and Luthien, Finrod and Beren come to Sauron. Felagund and Sauron strove with songs of power. "Then Sauron stripped from them their disguise...But though their kinds were revealed, Sauron could not discover their names or their purposes." The book states that Sauron attempted to keep Finrod to the last, because he "deemed that in him lay the secret of their errand."
My question. How did Sauron not know who Finrod was? Wouldn't he have known Finrod in Valinor...or was Sauron not in Valinor? What am I missing here? Any explanation on this would be greatly appreciated.