Talked with a GM already told me to post my problem here so here it is:
We've killed Sulfuron in MoltenCore, I was the MasterLooter, guildmember checked Sulfurons loot (before me) and she instantly received one of the loots. We didnt understand what happened she said loot was on GroupLoot for her but for the rest of the guild MasterLooter.
The one who received the item accidentally: Morgana
The one who should have received the item: Kerr
Raid ID: 715
Screenshot: http://prntscr.com/7hr50n
Notice 1 item received by Morgana and the other one still in the boss (Drop was 2x Pauldrons of Might)