If you've gotten to this blog post, you may be somewhat frustrated after selecting a backup to restore in iTunes, to then have iTunes report: iTunes could not restore the iPhone "Unknown" because the backup does not exist.
To which you may want to say: Well I was able to select the backup from the dropdown menu, so it must exist in some way!
I agree! Although you may also notice that the backup disappears from the selection menu after that initial error.
When you make a backup of your iPhone, iTunes stores some information files about the backup along with the backed up files themselves. I usually see this "backup does not exist" when there are problems with these information files among the problems with the backup.
Our software Decipher Backup Repair fixes issues in iPhone, iPad, and iPod Touch backups that cause this error message, as well as other error messages. You can download Decipher Backup Repair and watch a few videos about us and what the program does from our download page.