[Morsul the Dark]

Sauron assumed the ring had been destroyed.... Or so one would assume considering his lack of action over 3000 years. If he had been so agonized over its loss but knew it still existed he would have started looking for it much sooner, in my opinion.

I mean the wraiths supposedly could sense it when it was worn so they should have been sniffing around the misty mountains for those last 500 years when Gollum wore it constantly.

So no I don't feel sorry for Sauron because to me his actions seem to suggest he did not lament the ring.

Of course when he found out the ring still existed everything went to hell. but I think it was simply a loss of patience. He would have won if the ring remained unfound it just would have taken more time. He wanted two things his full power back and to protect the ring.

He (in my opinion) knew the ring was his only weakness, that is why He hunted it so desperately. He simply didn't think a hobbit would know how to destroy it. So that is why he moved on Minas Tirith and Saruman went up against Rohan. the two last bastions of power in Middle Earth.