First of all, you posted basketball in the football forum. It's cool...
Panini creates the card with the anticipation that the player will sign (stickers) and return them to them. They can't control the players willingness to oblige. Panini made a decision to send the cards out "as is". If you are unhappy, you can contact customer service and request a replacement, but since your redemption has now been honored, you may be out of luck.