Vishal Chaudhry's answer above worked for me. I would also add that in order to manually trigger the seque using:
[self performSegueWithIdentifier:@"mySegueName" sender:self];
from within the ViewController you must also select the unwind segue under the ViewController's Scene in the storyboard and in the properties view on the RHS ensure that the Indentifier field contains the namer you're referring to in the code ("mySegueName" in the example above).
If you omit this step, the line above will throw an exception that the seque name is not known.