Not sure I understand your post - if you went into a local Chapters, then isn't the instore computer, a database of what is actually physically in that particular store?
The Chapters website:
http://www.chapters.indigo.ca/ will let you search their pbooks, which you can order online (for delivery, not ebooks) or search to see if it's in a store near you.
If you're looking for ebooks, it directs you to
http://www.kobobooks.com.