Did Sauron think someone would destroy the ring or not?

From what I recall, one of Sauron’s major flaws is that he simply does not consider that someone would want to destroy the ring.

But then the other day, I saw this passage from In The Shadow of the Past. Gandalf says to Frodo:

‘And this is the dreadful chance, Frodo. He believed that the One had perished; that the Elves had destroyed it, as should have been done. But he knows now that it has not perished, that it has been found. So he is seeking it, seeking it, and all his thought is bent on it. It is his great hope and our great fear.’

Which implies that he does recognize the possibility of the good guys wanting to destroy the ring.