I know it is not permanent in the sense that buff is lost if you die...but the only other thing I was aware that removed the buff was a bug in act-1 arena. Since mine vanished in act2, I suspect the arena there might have same issue.
I'm just trying to find out why a buff with no time limit dissappeared on my character. When the buff was active, I did not notice any time limit on it...I cant check anymore since its gone.
The wiki page description of the buff describes it as permanent: http://divinityoriginalsin2.wiki.fextralife.com/Recipes
But since you suggested reading the description, perhaps you have a different link to online info about Attar of the black rose?