Unfortunately the triggering of the GotFocus event depends on the controls that are hosted in the RadPane. For example clicking on a simple TextBox would work, but with some other controls it wont do it. What you can do is, if possible to use ActivePaneChanged event instead of GotFocus as shown in the attache project. Also you can check simple implementation of selecting RadPane in a PaneGroup with clicking on its header. It would be great if you can check it out and let us know if this works for you.
Hope this will help.