There is a chance you've stumbled upon a small room with coffins in it - somewhere on the left, just above the middle of the map I think (it's guarded by a Golem IIRC). If you've killed all the vampires on the level, the most important ones (including Lassal) will go to those coffins to "recharge"; just make sure you have stakes and use them on the coffins - as soon as you've staked all three of them, Bodhi will appear.
