With extremely limited exceptions that apply ONLY if you were subject to DOT regulations and not always then, your employer has no legal obligation to verify employment. Sorry.
You might want to see if prospective employers will accept proof of employment by way of your W-2's or pay stubs; or if you can find someone in HR (who should be doing the verifications anyway) or a supervisor who can provide information for you.
Two things I am tired of typing: 1.) A wrongful termination does not mean that you were fired for something you didn't do; it means that you were fired for a reason prohibited by law. 2.) The above answer, whatever it is, assumes that no legally binding contract or CBA expressly says otherwise. If it does, the terms of the contract apply.