Advice on a "secret nest"

If you had a broody hen, she'd most likely have been on the nest. She wouldn't be leaving the nest to go to the coop at night, so you'd most likely have noticed if you were missing one when you put them up for the night. You can float them to see if they're any good. I personally would just dump them, but that's me. A broody sits on her nest pretty much all day, just getting up once a day for a short food, drink and potty break. She may also take a dust bath at the same time. Then it's right back on the nest.

 

I think you're fine. If you had a hen who had been sitting, you would have found her near or on the nest. Broodies also have this puffy, grumpy look to them so if none of your hens have seemed angry at the world, I don't think they've been sitting. My guinea hen has secret nests all over our property. What stinks is, is that when I remove the eggs from one nest, she gets angry and won't lay in that spot for the longest time. Who even knows where the new secret nest is xD

 

^ X3 Not a broody, just sneaky hens. I also wouldn't risk eating them, as you have no idea how old they are. I always crush and feed back eggs I find like this, to my hens (no I don't have problems with egg-eaters as long as they can't recognize it as an egg). You might also put some dummy eggs in your nesting boxes to get your hens used to them again.