If Dragoon K'naae ( -1373, 30, -1336 ) /waypoint -1373, 30, -1336 isn't up, it is possible someone killed him. Respawn time is 5 minutes (as of LU 43). This could apply to any of the steps of this quest.
Dragoon K'naae says that a weapon was dishonorably taken from him by Captain T'Sanne, who resides in the Citadel of Gul'thex ( 666, 0, -719 ) /waypoint 666, 0, -719 and requires that you retrieve it.
Usually when you arrive at the citadel, there is group of 4 skeleton mobs in the courtyard. You may need to keep killing them until Captain T'Sanne spawns. If so, there will be three waves once you trigger the spawn wave. This may take several rounds of killing the 4 skeletons. If not instant, respawn for the wave is 20 minutes. The wave is 4 lvl 30 heroic skeletons no arrows, or double downs. There is a chance that only 3 will spawn instead of 4. If a second group of skeletons spawns just after you kill the first group, you are on your way to T'Sanne spawning.
Upon returning to Dragoon K'naae with the weapon, you are attacked by three assassins (28v).
Protect K'naae by killing them (try not to use any AE spells or combat arts, unless it is encounter only, as you can aggro or kill Dragoon K'naae) and then speak with K'naae to complete the quest.