I do not know for sure, but two things cought my attention while we were there.
First, there was a lot of debris around the car, such as metal strap and scraps of wood (obviously not ties). So I wonder if another car, maybe a flat car, lost its load here at one time.
Also, if you look at the first posting, in the picture, I am standing on what appears to be the main line, and to the right seems to be a siding.... Although when I walked it, it wasnt more than maybe 100 yards long. The stock car sat where (if it was a siding) the western most switch would have tied back to the main. So it is possible if this was a siding, that the stock may have derailed on the switch, and just been left there.
Just a theory...
Casey