Of the Scriptural references to look to in terms of upholding Sacred Tradition:
1 Cor 11:2 hold fast to traditions I handed on to you
2 Thess 3:6 shun those acting not according to tradition
Also remember, that John wrote that not everything Jesus said was recorded (Jn 21:25).
The most important aspect of this discussion would be to remind our Protestant brethren that there was no Bible at the beginning of the Church. The Church, the bullwark of the Truth, is built upon Tradition, Apostolic Succession and guarded by the Holy Spirit against error. People were not handed a Bible when they joined the Church in the year 34 A.D., they were taught by Oral Tradition and through preachings of the Apostles and the designated priests and deacons of the early Church.