Perhaps our own Little Blue Nun can help!
2Corinthians 12:1~7: "If I must glory (It is not expedient indeed): but I will come to visions and revelations of the Lord. I know a man in Christ about fourteen years ago (whether in the body, I know not, or out of the body, I know not; God knows), such a one caught up to the the third Heaven. And I know such a man (whether in the body, or out of the bod, I know not: God knows): That he was caught up into Paradise and heard secret words, which is not granted to man to utter. For such an one I will glory; but for myself I will glory nothing, but in my infirmities. For though I should have a mind to glory, I shall not be foolish; for I will say the truth. But I forbear, lest any man should think of me above that which he sees in me, or any thing he hears from me."
We also know that Jesus' Apostles and Disciples spent almost three and a half years with Jesus, being taught daily, and yet St. John tells us in St. John 21:25:..."But there are also many other things which Jesus did; which, if they were written every one, the world itself, I think, would not be able to contain the books that should be written."
We know that some of this oral Tradition from Jesus to His Apostles was passed on to St. Paul, and others, also as oral Tradition. St. Paul obviously did not write down all that he learned from the Holy Spirit, or all that he learned from Jesus. As an example, the term, "Powers and Principalities" as in Ephesians 6:12 was only used by St. Paul. These are, from careful study, the two choirs of angels most of whom ended up as devils in Hell. We have to infir this because St. Paul refers to them as demonic forces. And in Ephesians 3:10, St. Paul places them in heavenly places. So apparently not all of them went to Hell, and were no doubt the choirs of Lucifer and Beelzebub (Apparently there were originally nine choirs and were reduced to seven. The book of Apocalypse mentions the other seven over and over again, once as the seven seals, the seven trumpets, and the seven last plagues. These are Archangels who are to the most powerful and trusted of the angels. So it's a match.) See also: These are the seven spirits which are before His throne, as in Apocalypse 1:4. These are the seven spirits of God as mentioned in Apocalypse 3:1 and 4:5.
If we add Traditions carried into the Church from the Jewish faith, St. Paul being a Pharisee of Pharisees, we can recognize from above four different sources of Tradition. None of which are captured in writing. First of all we have in 1Corinthians 2, Traditions received of the Holy Spirit both by St. Paul and the Apostles. In 2Corinthians 12, we have traditions given by Jesus directly to St. Paul, again orally and never committed to writing. We also have from St. John 21, that there were many things that Jesus spoke to the Apostles and Disciples that were never put in writing. Over the course of 2000 years of the Church, these Traditions, inspired, infused, or unwritten, have been woven into the fabric of the seamless garment that is the Deposit of Faith of the One, Holy, Catholic, and Apostolic Church. There is no way possible to identify these individual threads after this amount of time. (There were no protestants until 1500 years later. Therefore they do not have any of these Traditions. Therefore, when St. Paul says in 2Thessalonians 2:14: "Therefore, brethren, stand fast; and hold the traditions which you have learned, whether by word or by our epistle." Their answer had to be sola scriptura.
Of course, the above is from a Pre-Vatican II standpoint, as I am a pre-Vatican II Traditional Catholic, full habit and all. I wish to thank you for inviting me as it was a good refresher course. As you may or may not imagine, I deal with many people who are on the other side of this argument who are Novus Ordo Catholics who for the last fifty plus years have been trying to jettison these very Traditions. Especially as it regards the Holy Mass, Tridentine versus Novus Ordo. They have become oblivious to being almost giddy over sheading them to where the Mass and its embedded teachings are almost unrecognizable. Hope this helps.
Your sister in Christ.