[Sherlock declines to prod much further about how long John had actually stayed here. It was obvious there was a reason why he'd declined on saying so but Sherlock figured it would make itself known soon enough.]

Nothing.

So, I don't suppose that you know how what I can do works, do you?

[Just that he was feeling slightly better about this whole thing and that John was protected at least, in some ways. Sherlock was fiercely protective of John and this was just one less thing to worry about.]