I photographed this bridge on 4 July 2010. Photographs coming soon...
Web page for the trail. Photo 12 has a picture of the Warren through truss, which is possibly this bridge.
A rail-trail is being constructed between Osawatomie and Herington. Apparently, the stretch between Osawatomie and Ottawa is open and includes a Warren through truss. Based on Google Maps, I suspect that this is the bridge.