Come to think of it, we can't rule out the possibility that they actually did find God.
When asked for proof, he didn't provide proof, and responded to disbelief with punishment. That's very much consistent with the behavior of the Christian God.
Of course, this being apparently isn't omniscient and omnipotent, and the God of Abraham is presumed to be omniscient and omnipotent because... uh, because He said so, I guess. Well, maybe He lied. Why couldn't this being have deceived Abraham and Moses and the other prophets the same way he deceived Sybok?