Thats a tough one......if it was me and I knew the stand was on the property I had permission to hunt, I would go ahead and hunt it. If the guy showed up then I would just explain the situation. Tell him you have permission to hunt and that it looked like the stand had been there for years, just go from there. If he is adamant that you are wrong then i would apologize and find a new spot to hunt. Maybe ask the land owner about him.....