yoda sense by touch

Gently, Yoda reached and placed a small hand on Kenobi's. "Vos, saw I today. Acknowledged his aid through his unique skill, I did. Touched I his hand, through which flows the Force. Able at times, I am, to see that which is hidden. The Force was with me this day. The truth to me has been granted. Taken by the dark side, Quinlan Vos has been, though conceal it well, he does."

Dark Disciple, Ch. 34, pg. 246