There is another thing about that scene that struck me:
Irene drugs Sherlock, leaves her house via the window. Sherlock goes into his MP/drug trance whatever and solves the hiker case, leading Irene through it. He falls back into his imaginary bed, Irene comes into his real bedroom, puts the coat back, kisses him, disappears.
So we have a fluent passage from a drug state/mind palace scene to a real scene and we never see where one ends and the other begins. I find it very interesting how early Moftiss have started these things, building them up until the culmination in TAB.