In Medrash chazal, (including medrash raba, tanchuma, toras kohanim etc…) there is no mention of the Yom Tov of channukah. This took place 100-200 years before Medrash was written. Although it is hinted at (for example by Haman’s Gezeira he did not choose kislev because of chanukkah) Yet there is not clear story or halachic Medrash that discusses this. Did I miss something? If not why not? The first real mention is in Megilas Taanis and the Gemora. Thank you!
Welcome to Mi Yodeya! The truth is there is also very little about Chanukah in Mishnayos and Talmud. Some suggest that this is because Chanukah is specifically connected to Torah Shebaal Peh, so even though nowadays we are allowed to write it down, Chazal still decided to make Chanukah be written down as little as possible.