Why can’t I find the featured character in the Prayer of The Fleeting in the Witch’s Letter I got for my Bonus Rewards?

The Bonus Rewards you receive from the Prayer of The Fleeting do not include the featured character.

Other than simply pulling the featured character, they can also appear via the Prayer of The Fleeting’s “Guaranteed Appearance” function.

For more details about the differences between Bonus Rewards and the Guaranteed Appearance function, please visit the following link.
https://mementomori.zendesk.com/hc/en-us/articles/19406780742553