For the spell, it was indeed a problem of distance, as i checked with the grid , and the titan being in the bottom of the screen, it seems its distance to the target exceeded 30 cases.
For the titan disappearance, as reading again the hall of fame i see that this Tartarian titan is NOT having the amphibian icon and so maybe it can indeed have died IF he had actually retreated in the water (just a guess, i actually do not know why he died).
The Slave of Unreason disappeared too some turns after anyways and so ceased to besiege the castle.
I don't have the save of this specific turn, but in a very later turn , the titan (Iphianassa) is in the hall of fame confirmed as dead (and while i spotted no afflictions when he ran away, in the hall of fame he has 2 of them).
Notice the funny fact that the Slave of Unreason (Kurgi) is actually the leader of the Hall of Fame