Who watched the suitcase while Bud roamed the library?

The answer to this question can be found in the beginning of chapter 7 of Bud, Not Buddy. Bud has just arrived at the library because he wants to find Miss Hill and get some help from her. Once Bud enters the library, he narrates to his readers how much he loves the smell of libraries. He also gives readers some funny information about how mad librarians get if you fall asleep and drool on pages.
Bud doesn't immediately see Miss Hill when he enters the library, so he leaves his suitcase with the "white lady" librarian at the lending desk. He does this so he can wander the library without it while trying to find Miss Hill. Bud does not find Miss Hill, and he returns to the librarian that is present. Bud learns that Miss Hill moved away to Chicago.