How awful! I do hope it was just the heat and nothing more serious. It's certainly hot enough to be the cause.
Just a thought. I know we think that hosing down our dogs is a good idea, and I have done it myself. But while I was reading your post it occurred to me that this probably isn't such a good thing to do. The water from your hose will be very cold. What happens when we are subjected to cold water is the blood vessels just under the skin contract in order to keep the body warm. So you see it has exactly the opposite effect from what we want.
For children with high temperatures, and I imagine dogs too, it is better to use tepid water (i.e. body heat. I think dogs temps are normally higher than ours, but you might need to check that), perhaps from a bucket, and use a sponge or rag to wet Bailey with it.
Please don't think I am criticising you in any way, as I said I have done the same, and honestly hadn't thought about it very much until I read your awful account. Gosh, it must be so scary to watch your much-loved dog fitting so badly and for so long. Poor you and poor him.
(((HUGS)))
