The king in the mist doesn't drop the skull

Hi

I just killed the king in the mist and was surprised that he didn't drop his (+30 Spirit) skull... this is kinda bad to be missing on a minion since 30 is good enough to matter.

As I read the threads here, I think I am not alone with the problem, so please GGG clarify this for us: does he only drop his skull once or is this a bug.

Thx and have a nice one.