Last step of booster packs disappearing

2nd time this has happened to me. Opening the Walk on Wonders booster packs and after opening the 6th step for 1 coin, the last step which is the good pack, just disappears out of the store. Quite frustrating when I buy enough points for just the boosters now I’m stuck with enough points for the last booster but if I want another good quality pack, I need to spend more.

please help