Oh, that very thought only gives Childermass a brief flicker of dismay. He hadn't actually thought how how he would explain where the key came from, but now that Strange mentions it, he can only react by shaking his head. No, no, absolutely not.

"If you think I'll be telling them anything about this misadventure, you really are still mad," he tells him. "Mr. Segundus and Mr. Honeyfoot, perhaps, but maybe not even them. Better to let everyone assume I found it while searching the farthest reaches of the Raven King's kingdom than to bring up faeries, of all things."