Apologies for grabbing neither the game number, nor console log (I had one foot out the door). I believe it was one of the later maps in the "Rescue From Shieldhaven Prison" adventure, I had cast Path Of Knives on one of the dogs and when it moved and triggered, the roll for Hard To Pin Down was triggered succesfully - that caused the Path Of Knives to have it's damage blocked (fine), but it was then discarded and was no longer attached to the dog. Might be intentional, but I didn't read anything that would suggest Hard To Pin Down would remove the curse. I assume it gets discarded because it gets blocked, although my expected behaviour would be that the damage is blocked, but the curse remains.
Hard to pin down should only trigger when the card is cast not when the damage triggers if this happened then it is a bug