Joe! You may be onto Something Big here! Your mantis was conditioned to avoid the fake prey/non productive stimulus after ten tries. This response is very different from that of a cat that seems never to learn not to chase a lazer pointer dot (play behavior, there, perhaps?).
My guess is that when you repeat the experiment today, you will get the same response; the avoidant behavior will have been extinguished (he will have forgotten what he learned, just like I do!) over time. Now, this response stands in marked contrast to insects' and other predators' response to prey with aposematic coloration (red/yellow/ black, usually, like wasps and stinkbugs). There, the predator is believed to associate the distinctive coloration, after very few trials, with an offensive taste and leave all such prey alone in the future. This protection also extends to offensive tasting and pleasant tasting insects with similar color patterns (Mullerian and Batesian mimicry). So why the difference in learning time? I suspect that it represents the difference between a mildly negative stimulus (failure) and a strongly negative one (bad taste), but it might be that the reaction of insect predators to aposematically colored insects has been poorly studied (I am aware of one sadly flawed experiment from CA that any experienced mantis keeper would recognize).
When you have done all your tests with your mantis and the current learning situation, I wonder if you would be so good as to increase the negative/ avoidant stimulus, using the same subject. Set up a source of DC with a rheostat and try giving your mantis a tiny electric shock, nothing serious, just enough to agitate his antennae or tickle his tergites,* and apply it every time that he strikes at Rick's bug. I am guessing that he will learn much more quickly and that the conditioned behavior will not be extinguished over time. His avoidance of the harmless object after conditioning will also support Batesian theory.
I hope that you are as excited about this as I! I look forward to hearing your experimental results.
*If you hear a sizzling noise and the mantis stops moving, you have probably overdone things a bit. Try starting from the low end of the range and slowly increasing the power.