I recently shopped at Vyrso for "I Kissed Dating Goodbye" by Joshua Harris. It shocked me that this bestseller book was not available. I thought "what a poor bookstore that they don't even have this title."
Only later I thought that it might be available on Logos, and it was. However, these empty searches on Vyrso will probably leave many customers with a bad impression of Vyrso as a brand.
My suggestion is to provide a link to the effect of "Unfortunately this title is unavailable in Vyrso, but you can get it in Logos format here" or visa versa.