What do you mean doesn't show up in the reminders app? The whole reminder is just not there when you go into the app? Are you on the right reminder list within the app that has that particular reminder?
Interestingly enough, if you select the reminder in the notification screen when it alerts you, then close the reminders app the badge will show up immediately afterwards. Sorta useless unless you view your reminder and don't dismiss and just want the badges there to alert you that there is a reminder you need to dismiss. And I agree there seems to be some time period that passes that it will finally appear without doing anything. This has been an issue since iOS 6.