please tell me that i did not find a contradiction

Im confused. At the end of the Second Age Sauron was left behind on Numenor when Ar-Pharazon and his armada sail to their destruction at Valinor. It is said that when Numenor was swallowed by the sea that Sauron went down with it, and that since then he was never again able to have a physical body. But some time later in the Battle of the Last Alliance Isildur cut the ring from his hand. Can anyone see what im getting at? My only guess is that he was CLOTHED in a physical form like the Nazgul were when hunting for the Ring. Also, Glorfindel was said to have died in the Silmarillion when he cast himself into abiss with the Balrog, yet he is in the Fellowship of the Ring and in the Appendicies he went to war with the Witch-King of Angmar only a year after the fall of the capital of Arnor, Fornost, where he made the prophesy. But NOWHERE can i find an explanation of this. Was there two Glorfindels? Did Mandos grant him a second life as he did for Beren and Luthien? I don't know, PLEASE TELL ME!!!