That is basicly what happened. After about 30 seconds of players talking amongst ourselves to figure out what it was the DM said, "its a vampire." My response was "Vampires don't turn into dust!? Since when do vampires turn into dust?". Nearby we found large paw prints that went into the cave (we were told they were dog like) a lot of fur, and some humanoid tracks.DM: You see a thin layer of dust on the ground, it vaguely forms the shape of a human body.
Players (lacking the Knowledge(Buffy) skill): Um... okay. *whistle* Now what?
As for finding a sage the town we were near has no library or any real knowlege source, and the mage/cleric was killed off by the DM the session before. We did however talk to the Capt. of the Guard who thought this might be related to the problems in the grave yard we had solved earlier. However we had cleared the crypt of all but the invulnerable (DM even said that we weren't ment to be able to kill it) chained up ogre . The actual problems were solved when we killed a mage who had just sent a large magical crystal sphere into a portal. We have had no report on the status of said sphere.