IMO, I would take the stand down, and leave a note...waterproofed of course...If he has no right on your property that YOU have gained permission for then you have full right to treat it like your own. It is good that you spoke with the farmer first, because you never know if he has a relative that he gave permission to. You just alleviated a lot of problems. Again, leave a note with your name and phone number for the individual to call you. if in 30 days you don't receive a call, you just got a new deer stand.