Sorry to hear you lost your rabbit.
About 15 years ago, I lost 3 rabbits to heatstroke in one afternoon. The reason that I remember it, is that I just happened to be out there among them at the time. The rabbits were all lying as flat as they could get on their bellies, with their heads back, breathing rapidly. Suddenly, one rabbit began staggering around in her cage and screaming. I grabbed her, and rushed her to the garden hose, to run cool water over her in an effort to cool her down. While I was working on her, I heard another rabbit begin screaming, and a few minutes later, another. I guess by the time they were so distressed they couldn't be silent any more, they were in too much trouble, because I wasn't able to save any of them. Shortly after this happened, I built my current rabbitry, and included things like fans, additional shade, and a soaker hose on the roof. Thankfully, I have never had a repeat of that day.
A rabbit that isn't eating is a huge red flag for me. Your rabbit should have eaten something before the temperature got so uncomfortable that all he wanted to do was breathe. Was his water bottle working properly? Rabbits need water to process their food, so if they can't drink, they won't eat. I'm with RabbitMage on this one, I suspect there may have been something else going on: GI stasis seems a pretty likely culprit.
