We are going camping with our church next weekend, we simply can't go if he's like this!!!
It might work out that he sleeps better while camping - being constantly in the fresh air often knocks em out!
I'm sorry this is still going on for you. How's he doing now? What happened the day before the night he slept through? And what's your gut feeling (other than totally frustrated)? Is it a settling issue? Or a tiredness issue (under or over)?
For me, I think I'd try going back to square one, maybe sleep on a mattress in his room for a few nights and see if that helps, with the aim of doing Gradual Withdrawal to get out again.