Lost spell

Hi, I was on the quest called 'The Lich King's Command' and after I turned it in I few seconds later I had to use Death Gate to get back to the Ebon Hold. (QUEST 'Taking Back Acherus'). But on the loading screen I think the server crashed and when I got back in the game I did not have any quests in the quest log and after I took it again I realized that I didn't have the Death Gate spell but I did have the weapon from the same quest. After I walked to the Ebon Hold I can't turn the quest in.
Please help me salve this issue. Thank you in advance.

Frostwolf, Nazgrot.