I would base your appeal on the grounds that award being for 2016 NMF’s is probably because it’s intended for people going directly from high school to U of MN. I would then make the case that you are functionally in the same position. You’d be entering as a freshman, you haven’t been going to school anywhere else, you haven’t been working (assuming all those things are true). Briefly explain how your illness kept you from school or work; you’re not going for the sympathy vote, you’re explaining why you are in the same position as the 2016 grads. Definitely let them know that this is your dream school and that if you can afford it, you will definitely go. Good luck.