The Ring of Sauron

[Lord of Angmar]

The only logical explanation, Saucepan Man, is that Sauron left the Ring at Barad-dur during his stay at Numenor. That is what the following statement, taken from the Akallabeth, would seem to suggest:

But Sauron was not of mortal flesh, and though he was robbed now of that shape in which he had wrought so great an evil, so that he could never again appear fair to the eyes of Men, yet his spirit rose out of the deep and passed as a shadow and a black wind over the sea, and came back to Middle-earth and to Mordor that was his home. There he took up again his great Ring in Barad-dur, and dwelt there, dark and silent, until he wrought himself a new guise, an image of malice and hatred made visible; and the Eye of Sauron the Terrible few could endure.