Get service visibility

We have a number of image services in our Geocortex site and the user has the ability to switch on their visibility at runtime. These are ArcGIS image services.

How do we determine in a workflow whether the user currently has a particular image service switched on or not?

The image services don't have any actual 'layers' as such if you look at their REST endpoints in a browser.

I've tried using the GetLayerVisibility activity with the 'map service ID of the image service. This activity doesn't work without either a layer ID or layer name though.

What we need is a way to determine in a Workflow whether an image service is currently switched on in Essentials at runtime.