I don’t know if this has been pointed out by anyone else, but Sherlock hiding his cigarettes in the persian slipper doesn’t go unnoticed by John, in the beginning of The Hounds of Baskerville Sherlock checks the slipper and it’s empty.
Looking over to Sherlock, she sighed. “You were not supposed to see this. I’m terribly sorry, and I do apologize.” Her voice seemed to give off the impression she was anything but sorry. Rather, inconvenienced.
"I want to do it." Sherlock repeated darkly. "John erased me for a reason, and if I can’t know WHY… then I want to forget him in turn."
Stapleton furrowed her brow, setting the telegram down, “Our files are confidential Mister Holmes… so we can’t show you any statements or consultation records.” She paused, looking back up toward Sherlock. “Suffice it to say, Doctor Watson was… not happy, and he wanted to move on. We provided that possibility. I told him once that anything was possible here. I guess he lucked out; erasing someone or something from a person’s memory is surprisingly simple.” Stapleton explained. “Given the circumstances of this particular situation… I would be willing to perform the procedure on you. If you’re sure, that is.” She clarified. “It’s still considered experimental, but then again, almost everything we do here is.” She mused.