He certainly appealed to that as much, if not more, than to Holy Scripture. There is no conflict, of course; because everything he commanded the churches to do and to not do was in accordance with Holy Scripture; both the existing and yet to be completed Scriptures.
If all the answers were contained in the Scriptures, why did not Paul do like a good sola apologist and give them a list of Bible verses? It sure would have saved him a lot of time and effort; to say nothing of grief.
Because Paul received his authority and message by REVELATIONS FROM JESUS CHRIST, face to face and mouth to mouth. Just like Moses received his authority and message from God, face to face and mouth to mouth.
"..I have appeared unto thee for this purpose, to make thee a minister and a witness both of these things which thou hast seen, and of those things in the which I shall appear unto thee." (Acts 26:16).
"And it came to pass, that, when I was come again to Jerusalem, even while I prayed in the temple, I was in a trance, And SAW HIM SAYING UNTO ME..."(Acts22:17,18)
"It is not expedient for me doubtless to glory, I will come to VISIONS and REVELATIONS OF THE LORD."(2 Cor. 12:1).
"And lest I should be exalted above measure through THE ABUNDANCE OF THE REVELATIONS,.."(2 Cor. 12:7).
"For I have received OF THE LORD that which also I delivered unto you..."(1 Cor. 11:23).
"But I certify you, Brethren, that the Gospel which was preached of me is NOT AFTER MAN. "For I NEITHER RECEIVED IT OF MAN, NEITHER WAS I TAUGHT IT BUT BY THE REVELATION OF JESUS CHRIST."(Gal. 1:11,12).
Paul did not dwell on his own authority as per Rome, that of claiming infallibility when speaking according to his infallibly defined formula, rather he relied upon (in order below) conformity with Scripture, supernatural Divine attestation, and personal purity, unique eye witness testimony, and secondarily, apostolic confirmation by living apostles for credence, and his judicious invocation of authority was on the basis of the above, and it evidential manifestation.
(Acts 17:2) “And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures,”
(Acts 28:23) “And when they had appointed him a day, there came many to him into his lodging; to whom he expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening.”
(Rom 15:18-19) “For I will not dare to speak of any of those things which Christ hath not wrought by me, to make the Gentiles obedient, by word and deed, {19} Through mighty signs and wonders, by the power of the Spirit of God; so that from Jerusalem, and round about unto Illyricum, I have fully preached the gospel of Christ.”
(2 Cor 6:6-7) “By pureness, by knowledge, by longsuffering, by kindness, by the Holy Ghost, by love unfeigned, {7} By the word of truth, by the power of God, by the armour of righteousness on the right hand and on the left,”
(1 Cor 9:1) “Am I not an apostle? am I not free? have I not seen Jesus Christ our Lord? are not ye my work in the Lord?”
(Gal 2:6-9) “But of these who seemed to be somewhat, (whatsoever they were, it maketh no matter to me: God accepteth no man’s person:) for they who seemed to be somewhat in conference added nothing to me:..And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.”
(1 Cor 4:18-21) “Now some are puffed up, as though I would not come to you. {19} But I will come to you shortly, if the Lord will, and will know, not the speech of them which are puffed up, but the power. {20} For the kingdom of God is not in word, but in power. {21} What will ye? shall I come unto you with a rod, or in love, and in the spirit of meekness?”
(2 Cor 13:2-3) “I told you before, and foretell you, as if I were present, the second time; and being absent now I write to them which heretofore have sinned, and to all other, that, if I come again, I will not spare: {3} Since ye seek a proof of Christ speaking in me, which to you-ward is not weak, but is mighty in you.”
Because Paul was not an eyewitness of the events that the other apostles were. Further, and more importantly, He was not taught the gospel ... He received it by direct revelation. Read the first few chapters of his letter to the Galatians ... its in plain black and white.