Parshat תצוה is the only Parsha since the beginning of the Book of שמות that does not have Moshe’s name in it.
The reason for this was that when Moshe pleaded with Hashem to forgive the Jewish people for the sin of the Golden Calf, Hashem made him an offer. He told Moshe that He was willing to start all over again with him and destroy עם ישראל.
Moshe would not hear of this and told Hashem to erase his name from the Torah, rather than harm the Jewish people.
This is the reason we have one Parsha without Moshe’s name in it.
We also do not mention Moshe’s name in the Haggadah for a different reason. We do not want to deify Moshe into more than being a great man. Both the Parsha and the Haggadah actually indicate just how great a man Moshe Rabbeinu was. Shabbat Shalom