My duck hen got off her nest for about 24 hours near the start of her brooding. Are the eggs still viable?

She started sitting on March 2. On the 5th, she got off the nest for close to a day, then went back to sitting. None have hatched yet. We have a drake that I have seen mating with her and previously hatched out one of her eggs under a broody chicken, so I don't thing fertilization is the problem. Would the embryos die during the day she left the nest? She covered them with hay and feathers when she left them.