Hermione was desperate to get out of their house. Even for just a few hours, she needed to catch her breath and escape from the tension and stress that the unanticipated meeting with the Dark Lord brought crashing to her home days earlier. Unwilling to go to the Ministry of Magic on a Sunday even out of desperation, she left Antonin a note telling him where she'd gone. When he woke up, he hopefully wouldn't worry too much about her.