[obloquy]

I thought that Sauron could not take on the form of a man after he was swallowed up in the Numenoreans' downfall, but maybe I'm wrong.

He could and did. How else could Isildur have cut the Ring from his finger? He took yet another physical body after his defeat at Isildur's hand, and then moved into Dol Guldur and became known as The Necromancer. Perhaps you're thinking of this, from the Akallabeth:

And Sauron, sitting in his black seat in the midst of the Temple, had laughed when he heard the trumpets of Ar-Pharazôn sounding for battle; and again he had laughed when he heard the thunder of the storm; and a third time, even as he laughed at his own thought, thinking what he would do now in the world, being rid of the Edain for ever, he was taken in the midst of his mirth, and his seat and his temple fell into the abyss. 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,...

Sauron could no longer take a fair shape. But the paragraph I quoted continues:

...yet his spirit arose 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-dûr, 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.