All the joking and funny fixes aside, Roby you are, IMO, 101% correct. I have heard of such and in a number of ways.

Items that slowly changed my naive thinking about modelers being a bunch of really good people all with a common interest to enjoy a great sport/hobby started back when I was in my 20s. Items like: CL Stunt Contest: Had a special restricter in the engine venturi, went over for some lunch at close to site cafe, came back and getting ready for my 2nd official, I found the restricter had been removed. Some said XXX and friend had been seen *admiring* the airplane. I rammed a piece of bass wood into the venturi, got it running OK and beat his butt anyway.
Most of all, when I owned a Hobby Shop in Mt. Prospect, IL, Aero-Sports, I was very disillusioned at how RC guys that were supposedly friends would shop-lift. One even told me a sob-story about wife throwing his stuff away and leaving him. I sold him a new Kraft competition radio and 2 airplanes at MY COST. He wrote me a hot check and left the wife for a girl friend in Denver. Never collected on that. Hard to believe sometimes.
I knew of 2 ardent RCers that retrieved a Beginner's trainer from a tree while he was gone to get a ladder. They stole it. Why? How can one figure? They were both well beyond any need for a trainer. Finally it was found out, and one guy quit the hobby because of his shame and the other tried to join our club but was told "No Way". Have no idea where he finally went to.
There are thieves among us.