I agree with jk about the placement of surveyor's marks not breaking the time frame for an AP claim. No surveyor can act as an advocate for a client in the same sense that an attorney can, and therefore cannot act for the client in his place as someone breaking the claim.
The fact that the pins were yanked out without any consequences for the "yanker" just reinforces his claim.
As stated, the farmer must go to court to overturn the recorded survey. Sometimes a fence is just a fence. Sometimes a few strands of barbed wire will be run thorough he woods in the most convenient fashion, just tree to tree, following the boundary in spirit if not in fact. As to the law, AP is rarely a complicated issue in any state. The complication comes with the establishment of the facts of the case, as all AP claims revolve around the facts.