Can you lock them up for a few days? You could also go to an arts and crafts store and get some wooden eggs. Leave those eggs in the nest boxes. We got our wooden eggs in four packs. Also, I put my nest boxes in the darker corners, set the birds in them.. Not kidding. Just like you show a cat where to crap, I showed them the nest boxes. It only took showing a few.
Now admittedly, I still find the random odd ball nest. The last one was only 10 eggs, and that was behind a brooder box in my garage. The first one I found was during a hot spell, it was 22 eggs I think... Anyway, that was in a hosta. LOL. I candled them all then floated them to make sure they were all still eatable.
If the egg stay at the bottom - it is fresh. If the egg is at an angle on the bottom - it is still fresh and good to eat.
If the egg stands on its pointed end at the bottom - it is still safe to eat but best used for baking and making hard-cooked eggs. If the egg float - they're stale and best discarded.
I never use it: I feed all found eggs back to the birds, scrambled. Not that I get many rogue eggs. I'm quite the task master when it comes to laying in the coop!
We find secret nests all the time! We only have three layers so it's easy to tell when someone is hiding their eggs. It's just a matter of finding them! I don't even worry about checking them for freshness, we just eat them. As long as you don't rinse off the protective coating they should last a looooooooong time outdoors, even if it's hot out, right?
I did the Float Test- they all sank. Just to be sure, do you think an egg would still be good after sitting in the dirt in 80-90* highs for nine days???
ETA- does in matter what the temp of the water is?
Actually, yes they'd be fine. In other countries, it is unheard of to refrigerate eggs. And a chicken who is hiding her eggs may be considering brooding. SO, they fiind a spot that feels safe to them, lay a bunch of eggs, some other chickens may also find the nest, and deposit as well. AND THEN, the main offender disappears after she has a goodly number of eggs in the nest. This can take up to two weeks or more. And a lot of times, those eggs are in the dirt.. SO, they'll be fine.
My hen lays eggs in the flower bed sometimes. If there isn't an egg in the nest box, I go to the flower bed and VIOLA there it is!
I haven't been refridgerating my eggs recently. There was a time when a dozen eggs sat in a carton for 2 weeks or more. I float tested them, one of them floated just a tiny bit off the bottom, so I cooked it for the chickens to eat. I don't think it was bad, but all the other eggs sat firmly on the bottom. I also recently locked myself out of the chicken coop for a few days and I couldn't get the eggs, they stayed in the box for about a week. They're also fine, so I'm sure yours in the dirt will be just fine!
and @NovaAman is right, a lot of other places don't put their eggs in the fridge. Mexico doesn't, they have eggs out at the market in the heat and I'm sure they're fine. But Americans just go nuts for putting everything in the fridge! hahaha.