Twinkie's mom here.
I got an email from the breeders last night that said Donut passed away. He'd been healthy and playing fine - was scoping out an empty salad bowl after dinner (playing with the leftover carrot shreds) and fell over into it. He apparently had a massive heart attack and died almost instantly.
She said it was at least quick, her and her husband were both there and got to hold him, and he'd been healthy and happy up until it hit. They were pretty surprised, but glad that if it had to happen, it at least went that quickly.
Twinkie and I had a good cry over it last night.
So have a drink in honor of the Donut - the little guy was a real sweetheart.