Back when I was testing for worthy heroes I noticed him missing as well, so I enabled him in worthy heroes.
By the way a more effective way of testing is to set it up as a server game with all nations and set hosting to 1/minute. Just log in every ~100 turns and check which heroes are there.
A little problem are old age heroes, which can die without you noticing, but growth3 pretenders or modding the susceptible candidates to have nature magic fixes that.
Hmm, funny that the old Traitor King hero has been disabled. That sounds suspiciously like a statfix bug wrt national unit lists. I know for a fact that there is only one traitor prince unit type in the game and that one costs gold and is a recruitable commander.
Likely I have accidentally replaced the old traitor king with the traitor prince while adding heroes in dom3. Heroes are added in a new nationdata now that wasn't there in dom2.