Is it just me, or do they never actually expressedly say that Vandar has died? Sure, it's assumed that he died in the destruction of the Dantooine Jedi enclave, but in KOTOR 2, Vrook (I think it was Vrook, anyway) only mentions Zhar and Dorak dying during that time.
Personally, I like to think that Vandar managed to escape, survived, and is hiding a la Yoda, waiting for the right time to return... because he was the only really nice once.