I emailed liveaquaria last night when I pulled him out. It must've just happened when I caught him. His eyes weren't even "dead fish glassy" yet.
Everything that I've read about these fish says the two big issues are learning to eat frozen (which he did, plus picking at the rocks) and shipping. I was ever so slightly worried about him when I first put him in the tank, he sat on a trumpet skeleton for about five minutes, but he was swimming around for hours. I have a glass top on my tank. Could the lights turning off spooked him and he tried to jump and hit his head hard enough to hurt himself? I'm really at a loss here...