Sherlock at John's therapist's house

 (Sherlock meta by half-past-chaffinch)

"How did you know?! How? On Monday, I decided to get a new therapist. Tuesday afternoon, I chose her. Wednesday morning, I booked today’s session. Now, today is Friday. So two weeks ago, two weeks before you were abducted at gunpoint and brought here against your will, over a week before I even thought of coming here, you knew exactly where you’d need to be picked up for lunch?!" 

The 6th gif, though. Eurus is warily looking on as Sherlock says “I correctly anticipated the responses of people I know well to scenarios I devised. Can’t everyone do that?” Well, she can. She’s studied them long enough, she set her plan in motion, and here they are. She’s (supposedly) a Holmes after all.

Yet she’s nervous… she’s trying to make herself tiny, insignificant, unnoticeable. She’s a tiny bit afraid of being caught in the act.

But I suspect that if Mrs Hudson hadn’t had Sherlock thrown in the boot, throwing him a bit off his game (further than the lack of sleep and drugs already had), he might have caught on that something was off about the therapist. Maybe recognized her as “Faith”, maybe not. But he would have noticed that something was up.

Note that when he comes into the therapist’s house, he asks “who is this one? Is she new?” He had already researched the therapist when he figured out which one John would visit. He knew who the therapist was. So why did he ask “who’s this one? Is she new?” Sherlock recognized on some level that this was not the therapist. But he was too distracted (enjoying his scheme playing out) and rattled (from being drug addled and tossed in the boot) to pick up on things consciously.