Your very sentence denies "the only place His revelation to man can be found is in the Bible"... The Witness of the Apostles IS God's revelation - the Scriptures come to us FROM them.
For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost. 2 Peter 1:21
It is this speaking, as moved by the Spirit, that is God's revelation. You make a presumption you cannot possibly prove - that the Bible encapsulates everything that the Apostles spoke.
Regards
Peter says that the word is more sure than the voice of God.
And don't forget:
Psalms 138:2
I will worship toward thy holy temple, and praise thy name for thy lovingkindness and for thy truth: for thou hast magnified thy word above all thy name.
Who ever said that it did?
What God wanted later generations to know is what is written down.
We have a number of books cited in the Old Testament that did not make it into the Canon.