KIA Sedona warranty

Head gasket/radiator blew on 2016 KIA Sedona. I believe the issues should fall under the emgine recalls KIA but when I called KIA they say to bring proof of maintenance to the dealership. It's under 10 years old and under 100k miles. My husband does all the work on our cars but he did not keep a log, receipts, etc... How do I prove it was maintained over the years and get the repairs covered by warranty or recall?