Yes, statements can be sentences. For example, what I've just written is both a direct statement and a sentence. However, an indirect statement typically isn't a complete sentence. "That the booty was big" is an indirect statement, but it isn't a complete sentence. "The soldier was saying that the booty was big" is a complete sentence, containing the indirect statement "that the booty was big". I don't think "indirect sentence" is a thing (in grammar at least).