I am at a point where I am supposed to report back to "Yes Man" but he has vanished. When going after Benny I went the diplomatic approach and convinced "Swank" to support me in finding the scoop on Benny. Then I went on about my business as usual but when the time came to report back to "Yes Man" he had vanished ..... empty room no sign of where he went. What happened here?

He stands outside of the casino, follow your quest marker.

well, He change to NO MAN. so he is a goner.

He is the protectron with the goofy happy face outside the Tops. You passed him on the way up to Benny's suite.