'Some form of a Childermass' is fairly accurate, by the way. He is actually there, in some form, just not the one anyone might expect. A handful of things came back with him from Portland and it wasn't only a pair of jeans and a now useless cellphone, but the memory of another form, smaller, and even more covered in feathers than he normally is.

While he's been absent around the carnival as a human, he has been keeping an eye on Strange as a crow. When the man finally left to go speak with Lambert, it was only natural to follow, and now, here he is, perched near whatever window or hatch Lambert has cracked open to help deal with whatever fumes his laboratory may put out.

It's easy to eavesdrop this way, especially when you're light enough and small enough to miss easily.