: First, that Sauron did not realize that the Ring was still extant, and that he believed it was his own power, not the remaining existance of the Ring that had saved him from complete destruction, in the begining.

This is the only point that matters, as far as I'm concerned. The rest I agree with, more or less (I don't buy the "Aragorn appeared as Thorongil in the Palantir" argument, but that's beside the point). Your second point is actually not at all what Gandalf says about Sauron's motivations at the council of Elrond, and in fact all but contradicts it. But if you can live with that, that's your choice. And the final point, appealing to divine intervention, should be a last resort at most.

But as for this first point -- the key issue, you've now convinced me, is whether Sauron had really given up on the ring for most of the third age, i.e. really wasn't seeking news of it. I think you've made as convincing a case as possible. I still maintain:

(1) That he could have been seeking it and not known where to look (he had no sources)

(2) That the reasons to think the ring might still exist are too substantial -- (a) His own reincarnation (he should have at least suspected that this would not be possible without the ring) (b) The ringwraiths' continued existence (c) The fact that Barad-dur still had its foundations.

All appeals to 2000 years of forgetfulness or excessive focus seem to me thoroughly unconvincing.

But I will go off and weigh the evidence carefully. Thanks for the food for thought.