Not sure what your point is here. Scripture is not the beginning and end of Truth or the only guarantor of Truth or the entirety of all Truth. To say that would be idolatry. It would be attributing to a created thing, that which can only be attributed to God.
To be clear...you're saying God's infallible Word is not sufficient for us to know Him? Or have salvation?
John would disagree with you as would the Bible itself.
To allow this argument, that not all truth is found in Scripture, means you cannot deny any other belief system what they teach is false.
The Mormon, the Muslim, the Hindu, etc, all believe their non-Biblical teachings, as does Roman Catholicism to be inspired and truth.
There can only be on source of Truth. That is God. God has given us His written Word.
The Bible is replete with example after example of the appeal to the written Word as authority.
To allow other non-biblical writings to be accorded the same authority as Scripture opens many problems for the Catholic and has caused many false teachings to arise in Roman Catholicism.
14You, however, continue in the things you have learned and become convinced of, knowing from whom you have learned them, 15and that from childhood you have known the sacred writings which are able to give you the wisdom that leads to salvation through faith which is in Christ Jesus. 16All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; 17so that the man of God may be adequate, equipped for every good work. 2 Timothy 3:14-17 NASB
Again, ridiculous. Why not respond to what I actually said, instead of substituting your own words and then responding to that? I