I grew up in the country. Dad never locked the chickens up in the coop. We would often go years without a predator strike, but with no warning, something would find them and have to be dealt with. And once something found them, it had to be dealt with. I remember one fox being real hard to get. We lost several chickens to her before Dad finally got a clear shot.
Yeah, you were lucky. You just never know when they will strike.
Definitely poke around in dark spots, in and under nests, in corners, and such, but I doubt anything made it in and stayed without doing damage. Look up in the top for snakes if it is warm enough for them to be active. If something dangerous were in there, the chickens would have probably been on the roosts away from it, not on the floor. Some things like skunks, possums, and snakes would maybe be after eggs more than chickens, but skunks and possums will harm roosting chickens.