Yep, you are the second person reporting a similar issue.
I'm not sure what the problem is. Typically, I tell users to tap the Buy button and once AppStore starts downloading it then it realizes it has already been purchased and you'll get an alert about "oh, you've already purchased this so you won't be charged." (The is a design flaw in Apple's AppStore/update process.)
Since I'm not the store, I don't have access to any of your purchase records. Here is the App Store FAQ page and at the bottom is the email address for contacting Apple about your issue. http://www.apple.com/support/itunes/store/apps/