iOS UISplitViewControllerDelegate not being called?

[Ides]

I'm working on an app that uses the master detail template. I have a few different view controllers that may be used as the "detail view" depending on which option the user has selected in the "master view". Before I set a specific view controller as the detail view, I make that view controller the delegate for the splitview controller. I use the standard code in my delegate methods for having the "master" button appear whenever the masterview becomes hidden. If the iPad is in landcape mode and I turn it to portrait mode, hiding the master view, everything works fine. The delegate method is called and the master button appears. However, if the iPad is in landscape mode and the user hides the master view by tapping anywhere on the detail view, the method is not called. What could be the problem?