They seem pretty comfortable with all these odd places.
We've had three very successful clutches hatch on the shelf on the terrace, the buckets and hats (like a straw stetson) are very popular. The woodshed is about 75 metres from the coop so we were surprised to find one in there, she hatched out OK too. The PVC pipe was the most stupid of all, it was just a four inch pipe on it's side and she had tried to lay on the pipe - obviously a roundish egg on a round pipe needs more balancing than you're average chicken can manage so that was a bad choice. The daughters bedroom was a hen that she had played with as a chick a lot, when it was time to lay eggs she obviously thought that was a good place. Easy to spot though - a clucking hen and equally noisy rooster inside the house; didn't take long to find what room they were in. On the car is just plain daft - they know one of them, or sometimes both, will move nearly every day.
We had one 'disappear' and we assumed she'd been eaten by something, but she showed up three weeks later with a load of chicks peeping along behind her, she could've been anywhere.
Free ranging is like having Easter every day. If you don't find them, wait for her to disappear then count the days. It's a lovely surprise.