Go to the Tools menu and choose Options.
Click on the disclosure triangle next to Language Settings
Click on Languages
Is "Enabled for complex text layout (CTL)" checked? If not, check it and see if that brings the toolbar buttons back.
I think those buttons are only visible if CTL is enabled.
NeoOffice (app store version) OpenOffice.org 4.1 and LibreOffice 4.3 on Mac OS X El Capitan
OpenOffice.org 4.1.2 on Windows 10 (Previously on Vista)