After our writing group meeting last night, I accompanied Sarah to the Union Square Barnes & Noble to see if the book was on the shelves yet. We didn't see it downstairs on the New Paperbacks rack, so we decided to ask at the information desk. Sarah didn't let them know who she was, she just asked if "The Keeper by Sarah Langan" had come in yet. The woman at the computer, after asking twenty thousand times what the author's last name is and what the title is, finally located it in the system and, realizing it wasn't on the rack, decided the books must have been received downstairs but hadn't been shelved yet.
Luckily, I know the ins and outs of B&N unreliability, having worked at B&N myself, and told Sarah we'd better check the Fiction section upstairs before giving up. Sure enough, ten copies of the book were on the New Fiction shelf up there. I lent her my pen, a sales associate brought her some Signed By The Author stickers, and she signed away.
So if you live in the NYC area and want to buy a signed copy, head over to the Union Square B&N. Just don't bother asking any of the staff where the book is.