Photo taken by David Backlin in June 2011
BH Photo #202762
You are right--the bridge still carries a short length of track that seems to see use as a siding connected to the Missouri Pacific (now UP) line running N-S through town. The missing bridge in the middle was the Kansas City, Clinton and Springfield Railway, later part of the Frisco.
I don't believe this bridge to be completely abandoned. I live in Garden City and go to Harrisonville all the time. Most recently I recall seeing rail cars stored on this bridge over the summer this year, so I would think it still sees storage duty at least.