classifieds plugin - single-classifieds.php link to image gallery rather than the_permalink()

I was working on this issue in live chat with @aristath

using the code

I would like the thumbnail to link through to the image gallery lightbox rather than the page link.

Using this link as an example:

the user should be able to click on the thumbnail and a light box should appear. I have the lightbox plugin installed - you can see it working on the images below the description - but i would like it to work on the thumbnail.