According to the commentary in my Stone Chumash (p. 474) on Sh'mot, 29, from the 23rd of Adar, when the Yemei Miluim began, Moshe performed the sacrificial service and "had the status of a Kohen Gadol." On the first of Nissan, Aharon and his sons took over.
What was Moshe's status after that? Was he reduced to being a regular Kohen, or a Levi, or something else like a She'avar?
According to the talmudic discussion summarized here (yes, when discussing a Kohein Gadol who was temporarily disqualified, different from the case in Sh'mot),
Even though one may have only served as the kohen gadol for a day or two, he retains his exalted status as akohen gadol. While in terms of the Temple duties the original kohen gadol gets his job back, the backup kohen gadol would continue to wear the special garments worn by a high priest and be subject to the special laws pertaining to the kohen gadol, such as the prohibition to attend the funeral of a close relative or to marry a widow--once a kohen gadol, always a kohen gadol.
Rav Yossi disagrees and rules that the backup kohen gadol is "unfit both for the role of the kohen gadol and for that of a kohen hedeyot, a regular kohen". The Gemara explains that to have two high priests share the responsibility would be a source of constant friction, and to have one who served as a high priest relegated to serving as a regular kohen would be demeaning--violating the principle of "we go up in holiness, and we do not go down". It would be somewhat akin to the President of the United States becoming a congressman.
The Gemara follows with the ruling of Rabba bar bar Channa in the name of Rav Yochanan that the halacha follows the view of Rav Yossi, i.e., that the second kohen gadol is forced to retire.
If Moshe had the status then what happened to him? Were there any practical implications to the resultant status?