Currently Ishmael who had twelve sons has approximately 235,000,000 Arab descendants. Israel has “countable” 16,000,000. So did Yahweh lie? Gen. 22, Yahweh states Isaac is Abraham's only son so Ishmael cannot be part of the Promise. According to the above figures Jacob is missing at least 220,000,000 people today. Hmmm...wonder where they are or if I choose to deny this Promise, I call Yahweh a liar. Ouch! don't think I want to do that.
You do what you want. The expression "his descendants would be 'as many as the stars of the sky and the sand of the sea'" is a typical exaggeration you read in the Bible, so it cannot be taken literally. He was looking for them in Israel, not abroad.
The Jews were supposedly in the Sinai for 40 years, most of it one place, more than one million of them according to the Bible, yet they left no trace of their presence there, not even graves. So, something is not kosher here; you take a pick.
To suggest that the 10 tribes of the House of Israel disappeared and "became" Gentiles simply does not correspond to Jesus' mission and purpose on earth.