I don't know why anyone would think this impossible. As I picked up my daughter today from Kindergarten, I watched a small plane doing some kind of practice run over an empty field within one hundred feet of the school. He was flying so low to the ground, at times, I thought for sure he would crash. He must have made the same run 25 times that I saw and no one even acknowledged that he was there.
Ofcourse, the first thing I thought of was this guy could be syraying the school with something and no one wold ever know. This was before I read the article.
Flight training includes practice emergency landings in fields. Also, low altitude maneuvers simulating entering landing patterns, maintaining position in a circle over a point, etc. It is poor form to linger too long in one spot, scaring people or cows. That is what you likely saw.