I agree your scenario is most likely which is why I said an undeveloped egg would be better. But the OP said theirs are hatching so if they were brought straight to market, they could be fine. Normal eggs are tolerant a couple hours of off time so ducks can do a quick eat/drink/bathe occasionally. But as a rule, I would advise against it as in most cases you are right, the developing duckling would probably have died or at least degraded to the point it would likely fail shortly after hatching. I hope the OP lets us know what happens and if they hatch posts pics of the little darlings.(There are never enough 'ling photos in the world).