Not finding a Mo. death certificate for him. He may have died in Iowa.
The Edina Sentinel has a very good obit collection that they can search for you.
Looking for a phone number for you. Probably the easiest way to check.
Edina Sentinel 1-660-397-2226 Their collection starts about 1928 and is pretty current. If he had a Knox Co. obit, they should have it.