Related anecdote;
Two years ago I called Travellers to get a quote on insurance for my farm. Horses, cattle, chickens. When I mentioned 'chickens' the lady on the phone immediately said that "we don't insure farms with chickens"!!!
She didn't care if I had two, or two million; just "NO...
My outbuildings are all on my farm policy, and last summer when a big spruce fell on the coop and punched holes in the roof, it was all covered. :wee
Years ago, I found that my homeowner's policy would NOT cover my new barn, or horses, or any other livestock. Fortunately before a disaster...
So sorry for your coop, but how wonderful that the birds survived!
I too have electricity in my coop, and have done the best I can to make it as safe as possible. That's still no guarantee.
If that bucket heater was used according to directions, and still failed, I would be contacting the...