http://www.cardhunter.com/forum/threads/how-to-report-bugs.331/ First time I'm hearing this, do you still remember which adventure it was ?
I think I ran into this same issue, but I have to wonder if this is working as intended. I encountered this on the last battle of Melvelous the Magnificent, where one of the orcs (I think they were orcs?) Taunted a cleric. But the Taunt card attaches to your own unit, and I don't think attached cards go away just because the caster dies. The effect would still remain attached to your character, wouldn't it? In my case though, there were still multiple monsters left that shared a deck with the Taunter, and it let my cleric target the others still. It's also possible you have to kill all of the monsters sharing that deck before Taunt stops preventing targetting.
Yeah, so attached cards don't go away on the death of the owner. For example, if you get poisoned, you don't get unpoisoned if you kill the poisoner. It's possible we should write an explicit exception for Taunt.