Quest is bugged?

Hello,

I've encountered what seems to be a bug that doesn't allow me to hand in the quest I took from Vereth the Cunning. He is an undead DK NPC that hands you the quest A New Recruit and after that, you get to choose one of three quests, each basically includes killing a DK boss. I had no idea that I had to just take one of those quests but anyway, after I defeated Sapph at the icy overlook I wanted to go and hand the quest back to Vereth, the thing is that he wasn't there. I don't know why but If I fly into the direction of the Icecrown Citadel, he appears once I create some distance. From the distance I can clearly see that he is waiting there for me to hand in the quest, hence the question mark hovering above his head, yet every time I get closer, he disappears again.

I don't know if this is a bug or I am missing something.

Thank you,

Your humble Paladin.