No you're not, I had the same thing with my spears quest. I killed all 15 wisps and Marrec wouldn't give me the book. So I completely closed down the client and restarted it. Then talked to Marrec again and I got my quest finished up. I don't know if that'll work for you, but it helped me. Worth a try.
I think his problem is completely different from yours, since your npc is still there while ellie completely disappeared. Restarting the client won't make ellie appear.