The Jewish historian Josephus lived in 100 A.D. He said the ten tribes were still... scattered beyond Euphrates in his day, and were a great number of people, too many to be counted.
Some Jewish scholars do not try to scrap the ten lost tribes, and they do recognize their return in final, as written in Scripture like Ezek.37. So not all Jewish scholars scrap the ten lost tribes, or teach the falsehood that all the ten tribes blended back in among the Jews.
So much for any substantive argument you might think you have.
The only problem with what Josephus said is that it is counter to scripture. So who do you trust?
2 Chronicles 11:16-17
And after the Levites left, those from all the tribes of Israel, such as set their heart to seek the Lord God of Israel, came to Jerusalem to sacrifice to the Lord God of their fathers. So they strengthened the kingdom of Judah, and made Rehoboam the son of Solomon strong for three years, because they walked in the way of David and Solomon for three years.
2 Chronicles 15:9
Then he gathered all Judah and Benjamin, and those who dwelt with them from Ephraim, Manasseh, and Simeon, for they came over to him in great numbers from Israel when they saw that the Lord his God was with him.
And AFTER the Assyrian captivity....
2 Chronicles 30:5-6
So they resolved to make a proclamation throughout all Israel, from Beersheba to Dan, that they should come to keep the Passover to the Lord God of Israel at Jerusalem, since they had not done it for a long time in the prescribed manner. Then the runners went throughout all Israel and Judah with the letters from the king and his leaders, and spoke according to the command of the king: “Children of Israel, return to the Lord God of Abraham, Isaac, and Israel; then He will return to the remnant of you who have escaped from the hand of the kings of Assyria.
Archaeologists have studied the annals of King Sargon of Assyria and he only deported 27,290 people and 50 chariots.
And as I stated before, all 12 tribes were recognized as one. Ezra calls his returning remnant Jews 9 times and Israel 40 times. Nehemiah calls his remnant Jews 11 times and Israel 22 times.
By the time of the Maccabees, Jew and Israel had become synonymous terms.
And either Peter knew he was addressing both Judah and Israel or he was smoking something strange....
Acts 2:14
But Peter, standing up with the eleven, raised his voice and said to them, “Men of Judea and all who dwell in Jerusalem, let this be known to you, and heed my words.
Acts 2:22
“Men of Israel, hear these words: Jesus of Nazareth, a Man attested by God to you by miracles, wonders, and signs which God did through Him in your midst, as you yourselves also know—
Acts 2:36
“Therefore let all the house of Israel know assuredly that God has made this Jesus, whom you crucified, both Lord and Christ.”
Josephus does lend some insight on things but is hardly equivalent with scripture, except for those with an agenda.