Answer

It is hard to know. Already among the medieval authorities (Rishonim) there are statements about a few isolated verses that were added later. But in principle, it is possible that there were other such verses or passages, as the scholars maintain. I do not have a clear position. The presumption is that it was given at Sinai (or at least through divine inspiration) unless proven otherwise.

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Questioner:
Hello Rabbi, was the Talmudic text in the chapter—and the Oral Torah in general—also received by Moses at Sinai? I saw in Midrash Rabbah that this is what is written, and I understood that it appears elsewhere too…. And if not, I would be happy if the Rabbi could bring me sources..
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Rabbi:
The Talmud was received at Sinai? Where did you get this strange idea? In Sabbath 64, Rabbi Akiva teaches a halakhic ruling that had been accepted in the generations before him (that a woman should neither use eye paint nor rouge during her menstruation). Did the earlier version of the Mishnah come down from Sinai, or the later version? And did the rabbinic oath of inducement come down from Sinai? And the prohibition of meat and milk? And expositions and interpretations that are disputed and were developed over the generations? See the Encyclopedia Talmudit entry "Gezerah Shavah"; according to Nachmanides and his students, even a gezerah shavah that a person may not derive on his own did not really come down from Sinai.
At first glance, it seems that nothing was received from Sinai other than a few word explanations, a few laws given to Moses at Sinai, and a few interpretive methods (the hermeneutical principles, and even those not in the way we know them. See about this in my second book in the Talmudic Logic series on the hermeneutical principles of general and particular). The midrashim that say that both general rules and details were given at Sinai, and that everything an outstanding student would someday innovate, are only a normative statement and not a historical one (that is, that it is binding as if it were given at Sinai, or emerged from what was given at Sinai). Another possibility appears in the introduction of Tosafot Yom Tov, which distinguishes between "He showed it to Moses at Sinai" and "He gave it to him at Sinai" (but even "showed it to him at Sinai" seems strange and unlikely. These are merely aggadic midrashim).