You are correct!
Sorry for the error–this has happened a few times; I think that part of the problem is that the link gets chewed up and it jumps to the next…
While it is difficult to view everything in a linear fashion and find it in such, we can ascertain, from Church history (Apostolic Teaching and Apostolic Succession) that there are things that did take place that, while seemingly outside of Scriptures, is part of that direct lineage:
The relationship between the apostolic use of the Old Testament, for example, the Septuagint and the now lost Hebrew texts (though to some degree and in some form carried on in Masoretic tradition) is complicated. The Septuagint seems to have been a major source for the Apostles, but it is not the only one. St. Jerome offered, for example, Matt 2:15 and 2:23, John 19:37, John 7:38, 1 Cor. 2:9. as examples not found in the Septuagint, but in Hebrew texts. (Matt 2:23 is not present in current Masoretic tradition either, though according to St. Jerome it was in Hosea 11:1.) The New Testament writers, when citing the Jewish scriptures, or when quoting Jesus doing so, freely used the Greek translation, implying that Jesus, his Apostles and their followers considered it reliable. (https://en.wikipedia.org/wiki/Septuagint)
Of course, there would be those who would reject reason because of reason: if the Apostles had Jesus as their Guide, it tends to reason that their behavior (as in using the Septuagint) must have been conditioned by Christ’s practice.