This is covered in the "Tips and notes" for this section:
I don't understand why "Kdo mě hledá?" is not accepted. The Tips section doesn't explain when to use "mne" versus "mě" and looking at my table from Česky krok za krokem 2, the footnote just says that "forma mne je knižní" (ie, bookish/formal). There is nothing in the sentence that indicates a formal situation. Thanks for clarifying!