Why didn't Sauron feel the Ring?

Perhaps Sauron did feel the ring enter Mordor, but due to his pride or doubt that someone could WANT to destroy such a thing, he denied it. Or it could have been due to the fact that it was all based on a test of will. Sauron's will was searching for his ring, but Frodo had all of his will bent toward the ring's destruction. And remember, Gandalf said that Hobbits were amazing creatures, and that they constantly surprised him. So perhaps Frodo's will overcame Sauron's, or "shielded" the ring from Sauron's ever-searching benevolance..