Hidden Kobo books

I have noticed that there are quite a few books that are available for sale on the Kobo website but which don't show up in any search results.

For example, there are two editions of David Brin's The Postman that I can buy in New Zealand: the expensive, non-discountable Hachette UK edition; and the cheaper, discountable Random House US edition.

Only the Hachette edition shows up in the search results, but I can buy the Random House edition if I can find it.