Alright, I'm throwing in the towel. I tried feeding it sugar water, two flavors of Gatorade at room temperature, and a bouquet of cut flowers, and still he refuses to eat. Finally I brought him outside and put him on various things flowering hoping he'd do something, but frankly he's too weak to fly. I let him go. He was on a flowering tree a while, I left to plant some things, and then he vanished. So either he flew off, or a bird got him.