Some quests, do not show up - but this one is no quest. Please, look again => maybe you had the filter on and you see only unsolved ones (in blue?) Hit the "pin" in there => green ones should show up then. IN your case => the text should have changed to green, but you get no XP.
I've met the imp Taxlehix again, this time in the tunnels under the Academy. He told me about his uncle Nixfix who lives down here. Instead of simply showing me the way, he told me another riddle: * Where you level up - count back from 10 and stop at T - turn to your heart and look for me - you can't see, but follow your knee...* Crazy imp!
