Bilbo

From the text:

"His head was swimming, and he was far from certain even of the direction they had been going in when he had his fall. He guessed as well as he could, and crawled along for a good way, till suddenly his hand met what felt like a tiny ring of cold metal lying on the floor of the tunnel. It was a turning point in his career, but he did not know it. He put the ring in his pocket almost without thinking; certainly it did not seem of any particular use at the moment."