I now leave my Vox library on the "My books" screen and I check the "Preview" screen (by swipping sideways). It's just easy to see at a glance if a book has been erroneously placed there by Kobo. Now a completely different book is showing up there daily, and it's a purchase I made months ago, before I even had the Vox, actually. I just go to the contents, navigate to a point well within the book, close it, and the preview banner is gone. If I refresh, the book gets put back into its proper place.
I could ignore the preview banner, too, but I guess I just want to make sure I still actually do have access to the full book. Anyway, it's a lot easier than what I used to do, involving going to the Kobo website and setting a bookmark from there.
I no longer use 'preview' as a wish list. It's just easier to leave it empty so I can tell at a glance whether or not the Kobo software is being goofy. I'm putting my 'might read/buy in the future' selections on a list on my account at goodreads instead.
StPaddy, I've had this happen with 4 different books so far. For the past few days, it's been just one book that this has been happening with. Kobo tried to close my support ticket, I updated when the issue started with book #2, but they haven't responded and I've concluded they don't really know what to do about it. Oh well, it's minor, as long as it ain't costing me any $.
Oops, forgot to mention that they gave me a refund for the first book this happened with, although I didn't ask for one and didn't expect it.