Custom Plugin missing after 3.1.2 update

Hi Guys I run a cinema website for a client and got a guy to design a custom booking system for the site – the plugin is located in the left sidebar of the admin panel. after 3.1.2 update that menu has dissapeared from the left hand side although the plugin is working in the front end the site is http://www.moviejunction.ie ?? please help I cant get in touch with the designer (or is he avoiding me???)

Regards John