"Ah," the Doctor answers, giving not a single indication he's particularly taken aback by this news. In fact it makes perfect sense. It's a bit worrying, mind. Doesn't quite explain what's happened to him, either. And he just realises he can feel the rift around him. Weak, but still there. His time senses are back, that's more unexpected. Unfortunately he doesn't really remember how to deal with them, his memories being gone and all.

"I take it this happens a lot, then? Seeing as you're familiar with it," he asks. It would be a bit of a coincidence if he just happened to bump into one of the few people who know about it. Obviously it must be not entirely uncommon knowledge.