LOTR - A Long-Postponed Re-Read

[Inziladun]

Originally Posted by Elmo

I'm sure Sauron did not take his Ring to Numenor or it would have been lost when Numenor was destroyed. He left it in Mordor and took it up again after the cataclysm.

It is clear that Sauron did have the Ring in his possession when taken to Númenor.
Aside from the question whether Sauron would have felt secure enough to have the One Ring not only out of his sight, but across an ocean, Tolkien himself said:

[Sauron] naturally had the One Ring, and so very soon dominated the minds and wills of most Númenóreans. (I do not think Ar-Pharazôn knew anything about the One Ring. The Elves kept the matter of the Rings very secret, as long as they could. In any case Ar-Pharazôn was not in communication with them...)

Letters #211

I wish I'd known of that letter when I made my earlier remark.

As for how Sauron's disembodied spirit could have transported the Ring back to Mordor, Tolkien said in the same letter:

Though reduced to 'a spirit of hatred borne on a dark wind', I do not think one need boggle at this spirit carrying off the One Ring, upon which his power of dominating minds now largely depended.

Sauron was an 'angelic' spirit, after all, and even though he lacked a physical body, maybe what carried the Ring was his will.