I have had the same concern. When B&N did reply to this question for me, they told me that Pubit! doesn't choose which books B&N promotes. Unfortunately, It seems that bn.com is simply a virtual bookshelf that buyers can take your book from if they know what they are looking for.
I am currently having the same problem with the search engine. My title doesn't appear on the list, even if I use the words I listed in my initial set up with them.
I have had some success advertising locally with business cards, free book marks and posters.
I do thank bn.com for the opportunity to self-publish with them. Hopefully an agent or publisher will discover us one day.
That is something we'd all like to know. Read some of the other topics here.Keywords don't work either.