I have to respectfully disagree in my turn. Sauron didn't notice the Ring as much in The Shire because it was so far away. The closer it gets, the more connection he has to it (I sound like I'm talking about cellphones
). The Witch-King could feel it's presence in Imlad Morgul, just because it was there. If Frodo would put on the Ring, the Nazgul would discover him. Imagine what Sauron
would be able to detect if he was in the Witch-king's place!