As a backyard bird watcher in Lansing, MI, when someone says they saw a nest I automatically think cup shaped in a tree or cavity nester in a birdhouse. Of course the world is larger than my backyard, and interestingly enough, lots of birds have lots of different kinds of nests. Not all birds even build nests.
Some birds lay their eggs on a sandy surface. Other species will modify a nest site only slightly by scraping the surface of the ground or adding a few sticks or leaves around the eggs. Many birds dig a burrow in the ground to protect eggs from predators or keep them out of a scorching hot environment. A few birds even bury their eggs in decaying plant material and allow the heat of organic decomposition warm their eggs.
In mid-Michigan a lot of waterfowl (ducks, geese, loons, cranes, terns, gulls…) make nests or lay their eggs on the ground. And if you are near open farm fields, meadows, pastures, or prairies you may find meadowlarks, chickens, bobwhites, pheasants, or some species of sparrows raising broods on the ground. In forested areas some species of grouse, flycatchers, thrush, warblers, and more, are ground nesters and our Turkey Vulture will lay her eggs on the ground, on gravel of cliffs, or on logs or tree stumps in remote areas.
I've heard lots of customers' stories and have seen Killdeer and Mallards often coming into neighborhoods far from water to choose a nesting site. So a lot of birds will nest on the ground. I would need some more information to determine what bird made the nest you found.