Is he involved in a school extra curricular activity? If not, then he almost definately lied about the trip. But, you could ask him what class or group he went with. If he can't answer, then it sounds an awful lot like a lie, to me. And if he answers, just tell him that his father and yourself are going to go talk about the trip with the teacher that was in charge, because you disagree with how late they kept the kids out. That should take the wind out of his sails if he lied.
I could share with you a fairly sneaky trick I plan to use with my son. When he reaches the "privacy age," I plan to tell him point blank that I expect his room to be kept spotless at all times. If he doesn't do the job, I will. I figure it's a win-win. Either I get full rights to snoop through EVERYTHING he owns, or his room is so clean he'd never know if I snooped or not. It might sound a bit authoritarian to some. But, the ones that oppose snooping are usually either the ones with perfect children(a fairy tale), or are the ones more likely to have bigger trouble, in my experience.
As for the Quija board, those are not a big deal at all. They're just a toy. I think too much power for a kid's behavior has been given to games, like Dungeons and Dragons, Quija Board, etc. I have a hunch that he night have it in hopes of being able to communicate with his mom, though, which is the only way I can see the toy being a bad thing. Some counselling might prove beneficial for him, to help cope with his loss.
If his behavior gets any more erratic, you may have to bite the bullet and go through with a surprise drug test. You can even pick them up at the drug store now. If he's clean, then he'll somehow manage to get over it, in time. But, if he's not, then he really can't judge, can he. I would only consider this as a last resort, though.
