I rewatched "Best of Both Worlds" Part II last night, and noticed that Riker used the phrase to the crew. Didn't see him tugging on his shirt before sitting down, though.
It would have been eerie if Locutus had used the phrase, wouldn't it?
I watched this after "Sarek," and it was interesting to see two characters who were not Picard yet were, to different extents, composed of parts of his mind, call Riker "Number One." Are there any other times in the series when this happens? I wouldn't count BabyPicard and his "number one dad."