Well that's your story:
(New Testament | Mark 9:9)
9 And as they came down from the mountain, he charged them that they should tell no man what things they had seen, till the Son of man were risen from the dead.
What? This has to do with the Transfiguration,
which we know about it because is in the Bible, right there in the part that you are quoting, because of course Christ
did rise from the dead, at which point this injunction no longer applied.
This has nothing to do with anything being lost. What a bizarre conclusion.
4 How that he was caught up into paradise, and heard unspeakable words, which it is not lawful for a man to utter.
(New Testament | 1 Corinthians 3:1 - 2)
As I had written earlier, looking at things in context helps a lot. Let's look at this in its wider context:
1 It is doubtless not profitable for me to boast. I will come to visions and revelations of the Lord: 2 I know a man in Christ who fourteen years ago--whether in the body I do not know, or whether out of the body I do not know, God knows--such a one was caught up to the third heaven. 3 And I know such a man--whether in the body or out of the body I do not know, God knows-- 4 how he was caught up into Paradise and heard inexpressible words, which it is not lawful for a man to utter. 5 Of such a one I will boast; yet of myself I will not boast, except in my infirmities. 6 For though I might desire to boast, I will not be a fool; for I will speak the truth. But I refrain, lest anyone should think of me above what he sees me to be or hears from me.
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As our teacher St. Paul says, he is mentioning this man and the vision he had of paradise as a revelation of the Lord some fourteen years previous, showing that in such a man he will boast, rather than about himself. What in this suggests anything missing?
1 AND I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ.
2 I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able.
This is some shockingly bad twisting of scripture on the part of anyone who would take this to mean that things are missing from the scriptures. Lord have mercy.
Here is the entire chapter in question, which anyone who has eyes to see or ears to hear can tell is about not being carnal (in saying "I follow this apostle!", "I follow that one!", as though they are not all doing the same work), and again, is in no way about anything that is missing:
1 And I, brethren, could not speak to you as to spiritual people but as to carnal, as to babes in Christ. 2 I fed you with milk and not with solid food; for until now you were not able to receive it, and even now you are still not able; 3 for you are still carnal. For where there are envy, strife, and divisions among you, are you not carnal and behaving like mere men? 4 For when one says, "I am of Paul," and another, "I am of Apollos," are you not carnal?
5 Who then is Paul, and who is Apollos, but ministers through whom you believed, as the Lord gave to each one? 6 I planted, Apollos watered, but God gave the increase. 7 So then neither he who plants is anything, nor he who waters, but God who gives the increase. 8 Now he who plants and he who waters are one, and each one will receive his own reward according to his own labor. 9 For we are God's fellow workers; you are God's field, you are God's building. 10 According to the grace of God which was given to me, as a wise master builder I have laid the foundation, and another builds on it. But let each one take heed how he builds on it.
11 For no other foundation can anyone lay than that which is laid, which is Jesus Christ. 12 Now if anyone builds on this foundation with gold, silver, precious stones, wood, hay, straw, 13 each one's work will become clear; for the Day will declare it, because it will be revealed by fire; and the fire will test each one's work, of what sort it is. 14 If anyone's work which he has built on it endures, he will receive a reward. 15 If anyone's work is burned, he will suffer loss; but he himself will be saved, yet so as through fire.
16 Do you not know that you are the temple of God and that the Spirit of God dwells in you? 17 If anyone defiles the temple of God, God will destroy him. For the temple of God is holy, which temple you are.
18 Let no one deceive himself. If anyone among you seems to be wise in this age, let him become a fool that he may become wise. 19 For the wisdom of this world is foolishness with God. For it is written, "He catches the wise in their own craftiness"; 20 and again, "The Lord knows the thoughts of the wise, that they are futile."
21 Therefore let no one boast in men. For all things are yours: 22 whether Paul or Apollos or Cephas, or the world or life or death, or things present or things to come--all are yours. 23 And you are Christ's, and Christ is God's.
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People not being able to hear the message they are given because they're busy arguing among themselves over which of the apostles is the best to follow in no way leads to or even implies the conclusion that there was anything missing from the message. If my priest tells me 500 times to fast and pray and I don't listen to him because I'm busy with worldly garbage, does that mean that his message has been lost somehow? No. It's still the same message every time -- it is just lost
on me because of my own inability to hear it. He may try to say it in some different way, or to relax the requirements, or become more strict so as to make clear that this is much more serious than I am taking it to be, but in no case is his changing the approach so that I'll hopefully actually listen equivalent to the message being lost. He is preaching the same message throughout, it's just that when people are fools, or otherwise cannot handle what they are given, you don't just say "Nevermind, then". You still have a message to give, so you try to meet them where they are: milk for the babies, meat for the adults.