I haven't had time to read all the post, but what does your buddy say, after all it is his property. Is it posted all around, I would make sure the lines are posted for sure.

Did he shrug his shoulders and go back to reading the morning paper and drinking coffee?
Or, did get upset because the neighbor pissed him off before and call the guy names?

either way you are in a loose, loose situation to me. If you go up to the landowner and what next. Good morning, ect,.ect.,ect., i Think you should move your stand bla bla bla...... Might be a start to a wonderful relationship at first but will go down hill quickly once you bring his stand up. If you don't say anything, you might be in that stand one day and hear a shot... Then watch a great 10 pt rolling down the hill dead from the neighbors gun and kick yourself for not saying anything.

Good luck