That's one of the biggest issues with living in a smaller market.
They should sell you a revenue ticket to get to DTW and then get you the award seats for the rest of the trip.
I run into this issue when I want to fly from DC via JFK to get Oneworld awards to Asia. Since AA award space can be a bit sporadic on the DCA-JFK leg I sometimes have to pay cash. It's usually about $150 ow.