The verse quoted implores us all, as brethren, to “stand fast; and hold the traditions which you have learned, whether by word, or by our epistle.”
We are warned to remember the traditions which we have learned, whether by word, or by our epistle.
The day of the Lord is not to come till the man of sin be revealed. The apostle's traditions are to be observed.
Understand? The apostles traditions! DR further footnotes written and unwritten traditions of the apostles!
The fiction of "Revealed Tradition/Truth" came hundreds of years after Scripture was written in order to justify new doctrine which is clearly extra-Scriptural.