Does anybody have an pointers on completing the quest in which the guy asks you to help recover the painting of his rival/friend? I've run it several times with the same result, that despite recovering what is clearly the correct painting, all I can tell him upon exiting the mission is that I didn't find her or that I can explain.

So far as I can tell, there's no way to use the note he gives you to interact with the painting and confirm that it is the correct one. Picking the painting up does not trigger the quest to be marked as complete, and I don't know what to do besides consider it bugged and move on.

Has anybody been able to successfully complete this quest?