When was Sacred Scripture finished?
Who had the Sacred Scripture?
Sacred Scripture wasn't completed for a long time after Jesus was crucified and raised up. And, after it was finished, it took awhile for it to circulate everywhere and a lot of money to copy the scrolls. So...what did they do until even the Bishops and priests had all the Scrolls?
I point you to 2 Timothy 2:2: What you have heard from me, before many witnesses entrust to faithful men who will be able to teach others also.
Timothy is the second link in a chain of succession, and Paul is specifically is talking about three generations here, Paul's, Timothy's and, those that learn from Timothy.
What they did was pass down the teaching through two channels Apostolic succession and the people.
The Bishops taught future Bishops, and the Bishops taught the Christians the Gospel, and the "traditions." Now, you might ask what is this "tradition" where did it come from. Well, it came from Jesus. You'll ask me where it is in the Bible. Well, I have a question for you, do you think that all that Jesus did is in the Gospels? Or, do you think in the three years of his ministry and 33 years that the man may have done more than just what the Gospels say?
John 21:25 says, "there are also many other things which Jesus did; were every one of them to be written, I suppose that the world itself could not contain the books that would be written."
As we can see that it isn't true that every thing Jesus did is captured in the Gospels, there is oral teaching as well as witnesses. Witnesses are usually where a lot of evidence for our "tradition" comes from. When Doctrine or Dogma is put in place it has to match 1) the Bible and 2) come from the early Church fathers.
2 Tim 2:15 the word of truth: The gospel message, which is "heard" through preaching (Eph 1:13; Col 1:5). Uppermost in Paul's mind is the word of God orally proclaimed (1 Thess 2:13), not the word of God written in the Scriptures (Rom 15:4), though the latter is often central to Christian teaching and evangelism (2 Tim 3:16).