Your name is making me hungry.
I just started a brand new baby account and have also been unable to breed a Mist dragon. Any combination of blue and yellow will work, so if you have other dragons that have blue and yellow in them (which you must by now if you have been trying for Mist and having some failed breedings), try using them instead. You don't have to stick with just basic Water and Air.
Oh, I forgot - if you have Essence, you could also craft a Mist dragon. It depends on how badly you want to complete this event. Essence takes a long time to save up, so it is not to be parted with lightly, but I think Mist is maybe only 100 Essence, and if you are at level 38, you probably got the 100 gift essence for reaching a certain level or whatever.