To answer your last question first, yes, the rental agent and the cabin owner should have had all the facts before confronting the resident lady.

But, as a Chicago-area renter of a cabin on the TFF, just how would you have expected them to do so? Obviously, this turned into a "his word vs. hers" scenario, neither the rental agent or cabin owner were on site, all they had to work with was the explanation of the renter. Maybe, just maybe, the resident lady doesn't like renters invading her peace and tranquility of the TFF, there are many instances of locals not appreciating renters, unless the local happens to be benefitting from the rental (owns the cabin, sells bait, food or gas, guides, etc). I have no doubt the situation happened the way you've explained it, but without a picture of the (illegal) angler holding the fish, where's the proof?

HRG