A good question. Maybe he escaped yet didn't learn the culprit and thus whoever is behind it deemed it safe to leave him alive; he a pure blood after all, and not idly killed according to the vampire morals. Or maybe leaving him alone alive was intentional to begin with. Either way, despite being pure blooded, he can't probably go around killing everybody suspicious, so the culprits are relative safe most likely. Though where Yuuki fits in here is anybody's guess (despite my earlier post it's pretty obvious she has some deeper role; she's the main character after all. It would also be bit of a stretch if Kaname just happened to be there when Yuuki was about to be butchered by some vampire in the middle of nowhere).
We just have to wait and see. If we are lucky the plot is intriguing enough to make it worth waiting.