It's happened to me occasionally. Now I check and make sure the drop down menu next t the search box doesn't say, "All Products."
It didn't happen to me before but I have noticed that when I click on the author link to see what else an author has it bounces me out of the nook store every time. Paradoxically if you enter "Carolyn Keene" into the nookbook search it stays in the e-book section. "Nancy drew" will bounce you out even if the drop down says nookbooks.