I'm sorry for your loss. It's a good thing you try to figure out what's wrong.
My guess would be dehydration. If you did not have a mister/fogger, no source of water (since the bowl was dry) and somekind of ventilation (like a screen top of an exo-terra) combined with a UTH, there would not have been much moist in the air. These little guys come from Costa Rica where it's very moist and high humidity.

I would recommend waiting for more replies as well, someone might have another idea.