Nostalrius Begins - Quality wow vanilla realm (1.12)

Hi, my characters name is Krith on the nostalrius begins pvp server.I was doing the rogue quest for poisons. Earlier I obtained the tower key and logged off, when I logged back on the key was gone. I dropped and repicked up the quest, but now in my quest log it says I still have they key. But when i kill the defias drone he does not drop it. I cannot open the box at the top of the tower