Q: i submit my redeem code but i accidentally cancelled the downloading, how could i get my app back?

Does it show in the Purchased tab in the App Store app on your iPad for downloading ?

I did the same thing. No the app does not show up in the purchased list.

I was redeeming a featured app using a code. After entering the code, I received confirmation and it said preparing download, so I clicked done on the redemption page. I didn't realize that would cancel the app download. Seems like a terrible flaw to me.

When this happens you will need to go to your itunes store with your apple account logged in. Then go to "purchased" under "Quick links." Go to the app section, and check if the app is there. Click to redownload, and if it says that you have to go to the store menu, make sure you have your menu bar open in itunes, so that you can go to "store' and then click on "check for available downloads" and it will start loading. Plug in your device to your pc, and go to the apps tab after it has finished downloading. Scroll down the list of apps until you find the app you are looking for.