I also found what looked to be an egg in the "poo pile" in my leo tank. It had a hole in it and by the time I noticed it (thought it was poo) it had hollowed out and nothing was left inside.
Other than that egg the six ladies in that enclosure always lay in their moss box. I sugguest that you use spaghnum moss, my leos at least seem to prefer it over vermiculite. I think it's more natural. But that's just my experiance.
The ladies may know that they are carrying fertile eggs, but then again I don't speak geckoish so I wouldn't know. At least they seem to know what to do with the fertile eggs.