Ah the usual Mumsnet pile on. Usually consists of: you're an adult, and shouldn't expect anyone, not even your nearest and dearest to do anything for, or assist you with anything. You're an adult, and it is entirely unreasonable for you to need any rest or down time at any point, and if you do get some rest or down time, especially during the day, you are spoiled, pampered and entitled (or diabetic LOL). If your entrails aren't hanging out, or you aren't peri-arrest, you aren't really unwell, and even if you are, you shouldn't expect any help, sympathy or affection. From anyone. Oh, and the making up of random facts - the OP was drunk, her DH came to wake her after 15 minutes, the OP is obviously making all or part of it up, her DH is glad of the 15 minutes of peace.
Interesting psychology, to see a bunch of so called grown adults take such enjoyment out of mocking and being downright nasty to someone they've never met, who writes a completely inoffensive post on an anonymous forum. Makes me wonder how sad some people's lives must be to enjoy doing that.
Anyway, OP, it sounds like he probably did know you were asleep and left you there vindictively. Which isn't nice. For what it's worth, I did once get heat stroke from falling asleep in the passenger seat of a transit van, in the Uk in the middle of the day (shock horror), in about 28 degree heat. We had driven for six hours to get to our destination. I told the others (who were the ones who actually had an activity to take part in), that I was going to wait in the van for ten minutes and come out and watch them when the activity started. I must have conked out, and because they were taking part in the activity, they didn't notice that I didn't emerge. I woke up around 90 minutes later (so ok, longer time) my body drenched in sweat, my face dry and blisteringly hot, blinding headache, disoriented and vomiting. I did manage to get out of the van and make my way to the others, just before passing out and ending up in emergency for 8hrs being given fluids and electrolytes and ended up really unwell for about three days.
Yes it's unlikely that it would have reached that stage for you (as kids are unlikely not to come looking for food or something quicker than that), but you could still have ended up unwell and it wasn't a nice thing to do.
I live on another continent now where the temps reach 50 degree in summer, and if that had happened to me here, it's likely it would have ended up much worse.
Have a chat to your DH, OP and tell him you don't appreciate what he did, if it was in fact on purpose. And ignore the unkind people on here making things up to suit themselves.