I have no idea if anyone else has made this theory, all I can say is that I thought about his last night and wrote it down.
So in Troublemaker, Ladybug actually had one of her earrings taken off and half of her mask was de-transforming. The point of view from where we see it can clearly see her Marinette side of her face, but maybe Chat Noir saw it. But he probably didn't, otherwise there would be a reveal. This isn't an actual theory, just a thought wasted, LOL
;)