That is an interesting theory, I agree with it fully. I agree with if you use the same lure over and over again in the same spot on the same fish that eventually they will learn and quit hitting it, but i also feel that they have a very short memory. In many cases I have had similar instances as you had with the trout. Different species of fish though, from trout, bluegill, bass, etc. They will quit hitting if you stay in one spot and fish the same lure they do eventually learn and will quit hitting aggresivly, but I do firmly believe that they have little to no long term memory. Many spots i have fished until they quit biting, you can call it fish being spooked or learning, either way if I leave the spot and come back a couple hours later typically the bite will come back on the same lure that they quit biting before. I have even had fish that I had caught in the two hours prior get caught a second time.
I believe strongly that they do learn, as a survival mechanism, but there long term memory just isn't there.