Will Moshiach identify Jews currently thought to be non-Jews?

Question

The Rambam writes in Malachim 10:2:

ואינו בא לא לטמא הטהור. ולא לטהר הטמא. ולא לפסול אנשים שהם בחזקת כשרות. ולא להכשיר מי שהוחזקו פסולין. אלא לשום שלום בעולם.

[Eliyahu] is not coming to make impure the pure nor purify the impure, nor disqualify those who are presumed valid, nor validate those who are presumed invalid, only to make peace in the world.

He then goes on to say in 10:3:

ובני לוי מטהר תחילה ואומר זה מיוחס כהן וזה מיוחס לוי. ודוחה את שאינן מיוחסין לישראל. הרי הוא אומר ויאמר התרשתא להם וגו' עד עמוד כהן לאורים ולתומים. הנה למדת שברוח הקודש מייחסין המוחזקין ומודיעין המיוחס. ואינו מייחס ישראל אלא לשבטיהם. שמודיע שזה משבט פלוני וזה משבט פלוני. אבל אינו אומר על שהן בחזקת כשרות זה ממזר וזה עבד שהדין הוא שמשפחה שנטמעה נטמעה

Levites will be purified [by Moshiach] first and he will say this one is a Kohen, this one is a Levi and the remainder will be Israelites ... And he will identify Israelites only according to their tribes to inform that this one is from this tribe and this is from this tribe, but he will not say about those that are presumed Kosher that this one is a Mamzer and this one is a slave, because the law is that family that was buried remains buried.

Putting those two together, it would seem there is no point at which any Jews that have completely assimilated will be brought back, even if they have a direct line of Jewish mothers.

Does the rule of משפחה שנטמעה נטמעה apply there as well? Any decedents are treated as non-Jews in perpetuity?

Answer 1

Without consideration to the beginning of the days of Moshiach, if there is a problem, it will be clarified through resurrection. This is discussed in among other places, the second book of Sefer Avkat Rochel, section four by Rabbeinu Makir ben Abba Mori. An excellent source bringing the teachings of the Rebbe about this is Sefer Sha'arei Geulah, volume two which deals with the Days of Moshiach including the resurrection.

One of the side details about resurrection is that generally, those who depart last are the first to return. There are a few exceptions to this, but the general process is last to depart is first to return.

Part of this is in order that those still living will recognize the resurrected person who they actually knew as family. They are resurrected initially, exactly as they departed, meaning with the same outward appearance. And then afterward, their bodies are healed and perfected. It also increases the joy for each succeeding generation because they arise to see all their children and grand-children in front of them.

That will continue, generation after generation, back to the beginning. And in this way, there will be no doubt about anyones geneology. All those who seem to have been lost through the generations will be found.