"The problem fixed itself 5 days later (without giving me the in-app purchase)"
What do you mean? The only way this could be fixed seems to be someone giving you a refund, not "fixed [by] itself".
If you bothered reading the details about purchasing they have at the bottoms of those pages, they note that sometimes the animation for pack-openings will be skipped, but you can still check your Card Catalog and sort by "Newest" to see what cards you pulled.
If you were buying cards, then I suspect you actually did get the cards (but didn't know), and Konami thinks you're trying to cheat them by directly getting a refund from iTunes (but still keeping the cards).
anoymous
They are probably thinking that you were trying to game their system, try contacting them to sort it out. That is a really weird glitch though