Store stamps or store stickers on FCBD books will get you a green Qualified label. (Unless you request a universal label, then they may/may not honor the request: If they DO honor the request then then stamp or sticker will negatively affect the grade)
This is from experience, not just speculation. And from my experience, best case on an otherwise 9.8 (9.8 qualified) book is 9.0 as a universal with the stamp/sticker taken as "defect".
Next is speculation: I'd guess removing the sticker would result in damage or residue that would affect the grade more negatively than leaving the sticker and requesting a universal label.