Hi Mike.
I am sorry to hear about your experience – though it is both good and heartbreaking. Believe me, I know the feeling. My first pair to spawn simply could not get the eggs to stick in the cave, and one can say that if they cannot get them to stick, the eggs will be eaten. In your tank of the chocholates, (and I really understand that that makes it not good to have others around) but the paros also would have eaten the eggs most likely.
I think there can be different reasons for the non-sticking. Un experienced fish, young fish could be one. Wrong surface of the cave could be another.
Also the water qualities can play a role, as far as I know expecially the conductivity – but I am not totally sure about this.
My fish who couldnt get the eggs to stick went on for weeks, and I tried everything to help them, – in the end they succeeded, but it was quite a struggle.
So what you have to do, is simply to let them try again, and change some of the things around your tank. The good thing is that with paros, once they have started, they will definitely spawn again 🙂