i was looking through the lists of unique items on UESP wiki and i saw this helmet, it says its found in the labyrinthian, but i went through that entire dungeon, and i did the staff of magnus quest, too, i got all the notable loot EXCEPT this helmet!

it looks awesome, and i really want it for my collection, so could anyone help me find this thing?

It can be found in a corner behind a locked gate in the http://elderscrolls.wikia.com/wiki/Labyrinthian Tribune, during http://elderscrolls.wikia.com/wiki/The_Staff_of_Magnus.

does it have to be DURING the quest? i already completed it quite some time ago... months ago, actually... and i only recently learned about the helmet.

can i go back and find it now, or is it too late?