I'm sure it's in the game and the drop is random.... however multiple people not having this particular one forms a pattern. Maybe the drop rate is supposed to be like 2% and some programmer misstyped 0,2% XD
I think the drop rate for that is bugged. Something seem off about it, i have all schema but this one.. mostly everything is perfected. I run void everyday, and twice a day during event.. still no sign of it.