I've got an API that should return a single resource, but the method of specifying the resource is complex enough that shoehorning it into a GET request query string doesn't make sense, so instead we use a POST and have a representation of the query in the body.
Given the resource is just /resource/search, with no parameters, what should the response be if the specified resource is not found? If the result was an array, a 200 with an empty array body would be fine, and if the resource was specified in the URL then a 404 would make sense, but I'm not sure if the resource being specified in the body means a 400 or similar is correct?