Safe to say, that isn't the reaction he was anticipating. It's... him? That's enough to give Childermass pause, which involves eyeing Miko warily and trying to figure out if they had met directly before or not. No, is his conclusion, as Lambert had kept him apart from everyone else while at their place as a bird.

So then how?

In the end, all he can really do is frown at her and ask, "I don't believe we've met before, Miss...?"

Silver lining, that gives him an easy way to figure out which M name she happens to be.