I would contact the airline immediately! Surely, since the rule changed
after you flew to Japan, and they allowed your baby on the trip over they will make an exception and allow the return? We have flown with Toto many, many times and never had this happen. I would never, ever allow her to fly cargo .... it would be too hot/cold and traumatic! Stick to your guns and hopefully they will be cooperative. Good luck and please update us!