Was There Really an Epistle to the Laodiceans as Stated at Colossians 4:16, and, If so, Why Is It Not In Our Bibles?

Was there really an epistle to the Laodiceans, and, if so why is it not in our Bibles? Some scholars maintain that the letter to the Ephesians was not specifically to those at Ephesus but rather it was a general letter to the Ephesians and the Laodiceans, mentioned at Colossians 4:16. In addition, they say, is that the words “which are at Ephesus” found in most translations of Ephesians 1:1 are an addition to the text. They argue the letter that we know as Ephesians was a general epistle sent to the churches in Asia. Are they correct?