I purchased the Mighty Eagle, but now it's gone. Do I need to buy it again?

If the Eagle has disappeared from your device, you can download it again for free. Click the shopping cart from the game to open the shop and scroll to the right. Once you see the blue Eagle eye surrounded with green arrows, click it and you will be asked if you wish to restore purchases from your iTunes account. Select yes and fill in your account info (if asked) and your Eagle will be added back to the game. Of course you must be using the same iTunes Store account (Apple ID) to get it.