Normally I download apps directly on my iPhone. In this case, I got a promo code for Arctic Shuffle, so I was downloading it in iTunes on my PC, when iTunes froze--as it sometimes does when it's working a lot. I restarted the program and a) no app b) it says the code's already been used Great...
It's ok... Just download it as if you were about to purchase it and then it should say you've already purchased it and it's free to redownload. This exact scenario has happened to me as well and it was fine when I tried to then buy it...
It's giving me the "Are you sure you want to buy and download 'Arctic Shuffle'?" message. Does it still do that, even though it's about to let you download for free?
Yes. And then once you hit ok, it'll say you've already bought it. I know, it's scary taking that leap of faith. As long as you know you used the code (or began to use the code) and iTunes started downloading, you're good to go.
Try to write a review for the app. If it lets you, you can download it again for free. If it says you haven't bought the app yet, then your screwed. This would be if you got the promo code off a website and someone beat you to it.