There is no missing episode in the Viridian Collection for Fullmetal Alchemist: Brotherhood.
The Viridian Collection includes all 64 episodes of the series, so you shouldn't be missing anything.
However, there are some things to keep in mind:
* Different releases: There may be differences in the number of episodes depending on the region and format of the release (Blu-ray, DVD, streaming).
* Episode titles: Some releases may have slightly different episode titles, which could lead to confusion.
* Missing extras: The Viridian Collection may not include all the bonus features that were included in the original release.
To double-check, you can:
* Refer to the episode list: Check the episode list on the official website or on the back of the packaging.
* Compare to other releases: See if the episode list matches other releases of the series.
Let me know if you have any other questions!