Can't complete quest (The Way Forward)

So, a friend and I were doing the main story quest and i had to run back to the town. when I came back to meet him, he already finished the quest (killing the guards for the key to the thaumetic seal). I tried to do the quest, but it said i also need the key, which isn't anywhere on the loot drops. I logged out to see if it reset (and didn't rejoin him in party), but all the mobs were still dead and it still requires that I have a key. I exited the game completely and logged back in and have the same problem. Please help

Make a new instance by holdinding down CONTROL when clicking the entrance(door or waypoint) to an area.

You can reset the zone by ctrl-left-click the waypoint map or on the entrance to the zone itself. Then go and kill the guard at the passage again. He should drop the emblem for you.