I would be calling every vet in the phone book, first of all. My suggestion as far as getting your horse up, when all else fails, would be ONLY 1 or 2 VERY QUICK touches with a Hot Shot or Cattle Prod. If the horse is still down, put the prod away, your horse is probably not physically able to stand. I know this sounds extreme, but so does your situation. I do agree with Spastic Dove, though. Unless your horse is that laid back (unlikely), I think he would be up by now.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown