It's possible the nest got contaminated and the eggs went bad. I had a Broody toss an egg out so I put it in the incubator with the rest of the eggs I was hatching, turned out it was a deformed chick. When all babies were hatched I gave them all to momma, she rejected 2 that were the same breed as the bad egg.
Wow, I've only been raising chickens since 2014 and I've never seen a hen toss an egg or abandon eggs for this matter. Several factors coincide with these situations. Eggs get dirty and contaminated due to farmer neglect and poor coop design. Chickens are better off if one provides them ample space and cover and they'll keep up their numbers on their own. Their living area must be maintained though.