the only time i see my cranwelli burrow completely was when he was young and i would clean his tank with him still in the tank,my guess for this is stress, but i could be wrong, i now no longer do this as i usually clean my tank every other week now, and i use this time to set my frog in warm water so he can make poopie, anyways do as you said, leave him be, and try offering live food items every other day until he decides he is hungry