Your only way to get it back legitimately is either...
1) Go back to IOS6 and install it - this is what Apple expects you to do...
2) Install the previous version which will be in your PC iTunes app folder, assuming you use a PC to sync once in a while.
If you don't use iTunes to sync / backup your apps once in a while then you are going to be stuck. Apple policy is that they see no good reason for all device owners not to be on the most recent version of IOS when they restore. They simply don't support downgrading and this is one of the ways that they can catch you out...
Worth noting - It's a really good idea to sync your apps onto your PC for this very reason! If you get an update you don't like then you can always get the last version back!