It could be you made a mistake or the farmer drew a bad map (unlikely but I've seen people draw maps that are hard to follow) OR, you were set up!
You might at least talk to the farmer. At least by that you might be able to tell if a mistake was made or if you were set up. Either way, you'll still have to pay!
There's not much in life thats "fair!" Some minor "mistakes" are instantly fatal! This one just cost you money, live and learn!