I think I have this pretty well planned out. I have one additional neighbor who I might ask because he was arriving as I was leaving and going out when I was coming home. He's a nice fellow, retired form FedEx, and lost his wife a couple of years ago. If he saw anything, he would surely tell me.
I won't call names, but I think it was my next-door neighbor who helped himself. His house is about 400 feet from mine with a gully and trees separating. I once pulled a 20' container for him about 40 ft with my tractor when it was new. I've also pulled him on his father's tractor out of the sandy creek behind our places. He is just the kind of guy who thinks his need constitutes a good reason to help himself. I've observed scraps of poached game on his property with buzzards circling. He's also the one who bottle fished all the big catfish out of our lake because, "I gotta feed my family." There is no fence between our places and he could easily walk here and take my tractor after seeing us leaving at noon. If some neighbor had caught him and asked, he would have told them that he has my permission. That's just the kind of guy he is.
I'll do the light and I plan to install a four station video monitor. The next time this happens (if it happens) I'll have the perp on candid camera. In the meantime, I'm locking up keys, setting the disconnect on my TLB and pulling the 40 amp main fuse. The rubber cover for the breaker looks completely normal with the fuse pulled. The long-term solution is as Ron Hall suggested. I have to get off my duff and get my pole barn built. Unfortunately, if they break into a building while I'm gone, they would be hidden from view of the road. It's always something and a good insurance policy is the best plan.