Until the last few years I had never heard of the Lost Tribes of Israel.
As author Zvi Ben-Dor Benite presents, until the last few centuries the Lost Tribes were an incredibly popular subject; mentioned by the likes of John Calvin, Thomas Jefferson, the Israeli Parliament, Herman Melville, a 19th century theatrical parody, John Milton's Paradise Regained, and Theodore Roosevelt, among others.
A little background information:
The sons of Israel (better known as Jacob) comprise the Twelve Tribes of Israel. Through the reign of King Solomon the tribes were united as one nation known as Israel. When Solomon's son Rehoboam became king he became so harsh that the ten northern tribes revolted and the House of Israel was split in two. See 1 Kings 12:16.
The northern tribes--Ephraim, Manasseh, Reuben, Gad, Dan, Naphtali, Issachar, Asher, Simeon, and Zebulon--were known as Israel, and the southern tribes of Judah and Benjamin became known as Judah. (Levi doesn't have a land inheritance but they mostly stayed with Judah.)
This is why when you read in Kings and Chronicles it will say, "During the reign of ______ King of Israel," or "King _____ of Judah." I'd always thought Israel could be used interchangeably with Judah—like America or United States—but they are separate kingdoms!
So why are the tribes lost?
Around 740 BC Israel (the northern ten tribes) were taken captive by the Assyrians. This is seen in 2 Kings chapters 17 and 18, and 1 Chronicles 5.
Around 605 BC, Judah was also taken captive, but this time it was by King Nebuchadnezzar of Babylon. Judah was captive for 70 years and then returned to their land. The books of Nehemiah and Ezra discuss the return of the exiles to the land.
The Ten Lost Tribes: A World History is filled with fascinating stories of adventurers who searched the earth for the Lost Tribes. They believed they would find them in a specific, hard-to-reach place (the Island of Atlantis, perhaps?), and that they would be obviously Israelite.
Unlike the southern tribes the House of Israel never came back from the exile. They assimilated into the nations and forgot their Israelite identity. Certainly, there are hundreds of millions of people today who have descended from the Lost Tribes, but have no idea. YHWH promised Abraham that his descendants would fill the earth, and there must descendants from the Lost Tribes in every nation.
There are shreds of Hebrew evidence around the globe. The Ten Lost tribes recounts the story of a Marrano Jew named Antonio Montezinos travellin in South America in the 1600s. A local man named Francisco learned of Montezinos' background and offered to take him on a journey to "see your brothers." For one week, they crossed rivers and swamps in what is now Colombia. After resting on the Sabbath they reached a river on a Tuesday morning. Three men and a woman appeared by canoe, excited to meet Montezinos, and began reciting the Shema.
This book was a fascinating read, and much praise goes to Zvi Ben-Dor Benite for what surely must have been a mountain of research. This book is rich in insight for anyone learning of Israel's Lost Tribes.