Sirius might eventually put two and two together; Mary being so upset, Remus helping her out with Defense, and now this research for an unnamed girl that he couldn't tell Sirius about. Still, it was a Saturday morning and he had just woken up and he was too concerned about Remus to try to figure it out right now.
"Oh" Sirius said, coming out more like a question then anything else as he got up and crossed over to his nightstand, grabbing a piece of parchment to jot the title of the book down with a nod. "So, food and book. Just that one book?"