You can send us the email receipt that you purchased ARMS F&B and we'll restore your license for you.

If you couldn't find the email receipt you can also screenshot us the purchase history from iTunes: http://support.apple.com/en-us/HT2727


Besides that you can also provide us your Device ID of your iPad.

You can get the Device ID at Administrator > Upgrades > Select Upgrade button > Proceed until purchase screen (Device ID will be shown down there)