With the release of Sibelius 7.0.3 (available as a free update if you have Sibelius 7), the excellent Find in Ribbon feature is now more accessible.
This consists of a small edit box that is always visible on the ribbon bar, and which can be accessed by hitting alt then zero. You can then start to type the feature that you wish to find, and a menu will drop down with all the found options. Navigating through the menu and selecting an option should land focus on that control on the ribbon.
So, for instance, hit alt then zero, then type “Find”. This gives me a menu with several choices, firstly Find, then Find Next. If I navigate down to Find Next the Find drop down button is opened up, with the Find Next option selected on the menu.