Our youngest daughter ran away almost 3 months ago, same story from the local police. I suggest 2 things: Call the Kansas Bureau of Investigations, and leave messages for their son with the National Runaway Switchboard 1-800-621-4000.
The Colorado Bureau of Investigations has been very supportive and helpful to us. These state level agencies have access to methods of tracking your son that the local police either don't or won't use. They also may know private investigators that might help in your search.
The National Runaway Switchboard will encourage your son to contact you, and can arrange for a free ride home.
My prayers for a quick resolution...