is this the first year you've had them for mating season???
they are really good at hiding the eggd i noticed...
one of mine would lay her egg where ever she happened to be... befre i moved i found 4 eggs from her, in 4 different places.... and not in made nests either... hte middle of the walkway, under a tree, on top of the neighbors shed....
go on a serious egg hunt, or sit out latter in the evening and watch where they go...