"... it was. Of course you know that. I suppose that was his restaurant?"

It's a guess, but it seems a safe guess. Watson sighs, wishing desperately that Holmes, his Holmes, were here to help make sense of everything. "This feels like a terrible joke. What else can I ask you? Madame -- Doctor -- Joan, if you'll permit me the informality," because if you can't be on a first name basis with your alternate universe self, who can you be, "this goes far beyond mere coincidence, I am satisfied as to that. But I have no explanation, either."