Killed Lvl 80 Savannah Boss but died right after without looting

So, I killed Savannah Boss in an Irradiated map with a T15 Waystone (lvl 80 map).

I died right after due to a volley of arrows without looting the green item that awards 2 Boss Map skill points.

I just completed another map, Vaal Foundry lvl 80, and the boss has not dropped the green item that awards the 2 points.

Is it only dropped by the Savannah boss or is just bugged?

Appreciate your help!

Thank you.