I've only once found an egg that had been laid outside. I don't know if that is because I'm an inefficient searcher, or because they don't lay outside.
Chickens like solid, soft bedding (leaves slide around too much, for instance) in darker spots. Check old piles of insulation, hay lofts, etc. Mine like to lay in the top of the hay baler and in the horse trailer, and behind our pile of "swept hay" which is the loose stuff from our broken bales. Sometimes, a hen will tell you right where she's laying by singing the "egg song." Find her, you find the eggs (or at least the spot she's planning on laying the eggs.)
The smart, efficient route is to lock your hens in the coop and let them adjust to laying eggs in the boxes before you free range. I never do that.
