[HairOfTheDog]

Jen would be better for all these questions....

I don't think Sauron did knew Gollum had it, at least while he had it... 2500 years it was lost at the bottom of the river. Gollum found it and had it another 500 years or so... All that time Sauron was without form or power.

About the time Bilbo found the ring, Sauron was just beginning to take form in Mirkwood.... When he moved back to Mordor I do not remember, but Sauron was in Mirkwood still when Bilbo wandered through was he not?

Gollum, in his withdrawal and dispair perhaps wandered first into Mordor, they did not seek him out.

[Corin Stormhands]

I do not remember, but Sauron was in Mirkwood still when Bilbo wandered through was he not?

Was he? Do we read that in the histories? Or is it mentioned in The Hobbit?