This morning when I opened my game, I saw that my monster chest had turned into a green nature chest. I checked on my war and a couple of other things and then I saw that my nature chest had turned back into a regular monster chest. The nature chest was just gone! O.K. I did just wake up but, I know I saw it.
Now for the good part, six hours later I am playing the game and lo and behold! My monster chest has turned into a green Nature chest (I am filling it now).