Garage band app-file recovery?
iOS stores backups in two places:


iCloud - sign in to your account and see if a backup of the device is stored there. With the files app on iOS 11 and browsable iCloud storage on macOS this might be the easiest bet.
iTunes device backup or sync - check iTunes on each computer you may have connected it to recently, when you sync to a computer, it will make backups of your songs and other data
iCloud device backup - restoring an iCloud entire backup of the phone data might also get you the files back or so you can export them elsewhere.


http://support.apple.com/kb/HT4946