Oh - I tapped and wiggled the tub a little and his body just rocked in place. It wasn't until I actually opened the tub that he decided to move. I was like "great - I've never had one die on me (well, I've lost two normal hatchlings I've produced that never ate and fought assist feeds, but none that matured into juvie and adults). And he's been in the collection for a few years now, and he's not been behaving like he's sick or has had an RI (no rubbing the face or "sliming" his enclosure, or holding his head up to breath), so I was just baffled what could have killed him (he also wasn't on the heat, so I knew he hadn't been burned). Must have just been deep in sleep - wonder what he was dreaming about! LOL