Photo Gallerry by 10Web Not showing as an installed plugin

I’ve not used the site for about 18 months and have decided to start posting again.

When I came to look at the site, instead of the photos I should have seen there was only the shortcode [Best_Wordpress_Gallery id=”323″ gal_title=”Stags & Bucks at Studley Royal”] to be seen. when I investigated further the plug-in could not be found in the list of plug-ins installed on the site. I tried to re-install from the add plug-in menu but this was not possible as it stated the directory already existed.

I ran the Health check plug-in and that showed nothing relevant to the problem.

How do I recover the Plug-in and galleries?

The page I need help with: [log in to see the link]