Before I ever finished your post I though "Meth Heads" It is becoming a growing problem here in Oklahoma. They will trespass on other peoples property so that they won't get caught on thier land. From what you described (shorts, cold weather) he wouldn't have noticed the weather if he was all messed up. Also the fact he was hiding from you is suspicous. I think you did the right thing by making him think you didn't see him. I would definately contact local law enforcement and have them check the area out. And I wouldn't go back until I knew everything was on the up and up.