Prior to John's writings there were 22 books. What known bok written between those 22 and what John was going to write was known to be rejected for what ever reason?
Paul's letter to the Laodicea church? Any others?
Not sure of "rejected" or just "not inspired" so not included. I do not believe a single Word inspired by God is lost, but do believe the Apostles wrote many things that were not inspired so are not in the canon.
First letter to Corinth. We have the second and third (labeled I & II since the first letter is missing).
BTW, I personally think that the letter to Laodicea was a cyclical letter that was to ALL the Greek churches in SW Asia Minor. Oldest manuscripts of Ephesians literally have a "blank" in the name, so that copies could be made for Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia, Laodicea, Heliopolis, Miletus, Troas (Troy), Assos, et al. While Paul's letters often have specific people or events mentioned tying him to that specific city, the Epistle to the __________ (Ephesians) has none.