The Gentiles were never to hear His voice, that wasn't His mission. That was the Apostles.
Matt. 15: 24.
24 But he answered and said, I am not sent but unto the lost sheep of the house of Israel.
The sheep that would hear his voice and become one fold were of the house of Israel. John 10:16 is about OTHER sheep not of that fold.
The absurdity of your assertion is instantly revealed when you but look at yourself ... you are not a jew yet you can be ‘as a son of Abraham’ by spiritual adoption through the Grace of God in Christ. THAT makes you one of the lost sheep to be brought into the sheepfold, seven. Joe Smith was not a Jew, not a bloodline descendant of Abraham, yet you would claim he was chosen as an apostle and the Gospel of Jesus Christ (by the Spirit of Him) IS Jesus speaking to you to offer deliverance. Priro to His crucifixion, He was come only to the House of Israel. After His resurrection and Ascension He has been coming to the lost sheep like you and me.
Ya coulda FOOLED me!
NIV Luke 2:28-32
28. Simeon took him in his arms and praised God, saying:
29. "Sovereign Lord, as you have promised, you now dismiss your servant in peace.
30. For my eyes have seen your salvation,
31. which you have prepared in the sight of all people,
32. a light for revelation to the Gentiles and for glory to your people Israel."