1St Class Quest isn't working

I and one my friend are tryn to make 1st class transfer quest. But it seem's to be bugged. There is one mark wich drops from mobs inside dungeon but when i pick up it the item dosen't show up in my inventory.I should collect 3 for opening the door but i can't get even one becouse of that. Please do something about it.

Talk to the big thing in the center of the room. Do this three times after fighting enough to get some drops, whether or not they show in your inventory.

I agree this could have been clearer in the game, but it's not bugged.