Grocery eggs aren't even fertilized.
https://www.delish.com/food-news/a63842548/what-are-fertile-...
You will find a number of people who have claimed to have hatched a number of types of birds from store eggs, including chickens.
New layers are bred away from the main flocks in relatively tiny volumes, under 1% of layers' eggs. Culls may drive a need for more layers to be raised, increasing that percentage but the cycle rate for these hens in intensive farms is pretty regular already (<18 months) so I doubt they'd invest in the additional hatchery facilities for a temporary population lull.
this actually speaks to my point more than the other replies you (and other) gave. A temporary shed for layers to nest isn't insurmountable. Especially if you know that the end result is more money for you because of supply issues.
What i am not sure about, is why that didn't happen, since you say it did not. anyhow, it was just an idle thought. If i was selling eggs, and suddenly a quarter of my flock was wiped out - by a fox or something - i would probably immediately borrow a rooster and let the layers nest. I've done it before, so i'm not just "guessing." Contemplating protecting nesting chickens is the only thing that gives me pause, as i don't really like "outside dogs", but i have a herding dog.
