I believe that the file can be only found if you have access to the system folder of your iPhone but there's no way to access the system folder except for iPhone which is already jailbroken. But there is no jailbreak procedure that will work on the latest version of the iPhone yet.

I've also heard someone use iCloud to back up the wallet(Different wallet) but after he synced the backup wallet it doesn't show the old wallet. So it's not a good idea to backup your using iCloud.

If you want to backup your wallet like the above said it is always the best to have a backup seed phrase on the piece of paper or save somewhere safe.