Does your warranty state that it was required to have the 30,000 & 60,000 maintenance done? If it does, you have no recourse. If it doesn't, then you have a case. Somewhere you need to put in your wording that you never expected a 4 year old engine to die EVEN IF YOU DIDN'T DO THE MAINTENANCE. That says a lot about the quality of Kia. Heck, I trashed my cars in college and they kept on running!
On the other hand, Kia does not have a good track record of making good quality cars. If you notice, their cars don't stay on the road for long. That is why they are so cheap. You may have to chalk this up to a lesson learned... :(
I ended up upside down with a used Volvo. It stopped running and had 2000+ plus worth of work with another 2000+ expected in a year. It wasn't running and I still had over a year of payments. Lesson learned, the high-end cars (Volvo, BMW, Mercedes) lose their value quickly b/c the cost of fixing them is outrageous! My neighbor has had the same issues with her used BMW. We will never buy high-end again.
I hope things work out for you! Good luck!