How do you know he was there for only 15 minutes? Heck he could have been there all day just moved around to do a little scouting or maybe to stretch his legs. Now making excuses for the guy but it's possable.

As for the blaze orange well.... unless you got photo's it would be hard to prove as it would your word against his unless an officer saw him.

I have hunted public lands many times and am never comfortable there in rifle season and in bow season I have often moved or changed my area because of others. It happens and I agree with the others about the comment you made....You might or might not do something to his property but that statement would make you look pretty guilty if something did!