Unbearable whispers V not dropping the recipe "prefixes cannot be changed"

I have completed the prophecy twice, and the recipe that's to drop when you complete it is not dropping for me. I looked around the whole room, turned off my loot filter, and from those two occassions I even did the prophecy in different lab difficulties, but it did not dropped.

in 3.16 these recipe gotten rework in their location to make it much accessible for players to find them.

check http://www.vhpg.com/poe-crafting-recipes/
for the updated list