salth20cowboy, you bring up a subject that touches a raw nerve for many of us. In your case, it appears that the person thought they had permission when in fact, they really didn't. You're lucky, this appears to have been an honest mistake that was easily corrected. One thing we might all do is put up a sign saying "NO FISHING" right on our lakes. I just tell people that fishing is never allowed on our lake unless I am physicially present and their invitation was for one time only.
Other comments here appear to be just plain theft and should be handled as such.
People wanting to stock our lakes is a whole different problem. It appears that people everywhere just want to put fish everywhere. And everyone thinks they know more about managing our lake than we do. In our area, the problem fish are northerns. Some people think that every lake should have northerns.
The problem is really one of "frame of reference". Their experience is that of fishing large public lakes. They think that everything that applies to these large lakes should apply to our little lake. They think we should have everything these large lakes have. They think it is ridiculous to have to throw back good eating sized fish. And they certainly want to use their fishing tackle that is made to land fish, not to release them. I want these people on my side so I do a lot of explaining about why I do what I do. The thieves don't care of course, but I've been able to "convert" most of the others.