Voidcore Consumed Automatically

I would like to report an issue that happened in The Voidspire.

When fighting the first boss in Imperator Averzian (Character name Nevelust-Illidan, the fight was on Apr.28), I did not intentionally use an Extra Loot Roll, but my Nebulous Voidcore was automatically consumed. I only realized this after seeing the extra loot appear in my bag.

What is more confusing is that I no longer need any loot from the most of bosses on Heroic difficulty, so I had no reason to use an Extra Loot Roll there.

I am certain that I had closed the Extra Loot Roll window, which is why I do not understand how this happened.