Where is Paper Trail and Minister Spindle

[Zetix63]

Hi! I'm doing the "Rehearsal Roundup" quest, and I only have two ponies left to give sets of sheet music, but I don't know where are those two...
On the wiki, it says that Paper Trail is on the desk on the Crystal Castle, but when I go there,  I only find Rosey Quill.

Also, Minister Spindle is not on the front of the library.


So, where I can find those ponies? Thanks for the help!