Well, sometimes its hard to tell if he actually eats them or not. If your betta keeps collecting them without ever swimming up to the nest and pushing them in, then he most likely had a big snack! Since he most likely didnt get to fertilize the eggs (I understand you put him in with the female AFTER she started to drop eggs?), it could be that he is not that attached to them as if he had fertilized them....
I am sure it was a mating attempt, and it doesnt allways work out at the first try. Some females are swimming away from the male for hours and hours to come, until they suddenly decide that it is time to be affectionate. While some males are very aggressive toward the female before they actually start the mating process.
Anyhow, its very hard to recognize eggs in a huge bubble nest, maybe they are in there, and you just cant see them yet. Although if they are not fertilized, there will not much be going on afterwards. If they got fertilized, you will see some tiny fry hanging tail down from the nest after a few days (depending on the temperature).
It took me quite a few attempts and tests to figure out if and how it is the best of conditions to bring the male and female to successful mating.....
Let us know how it turns out!