Is there a way to determine via the LightcastAPI if media content is active or not?

The LightcastAPI only returns active media items, as its purpose is to allow clients to build a dynamic system for displaying their content. If you choose to deactivate content via your Channel Managers, then it will no longer be returned by the API.
 

How to deactivate/activate a Channel

In your Lightcast Media Cloud account go to "Channels" in the left-hand menu and search for the Channel you would like to activate/deactivate. Then click on the status which is shown within the "Status" column. If the status of the Channel is "active" and you would like to change it to "inactive", simply click on the status "active". This will turn the Channel into "inactive". 

If you would like to turn the Channel to "active" again, click on the status "inactive". This will turn the Channel into "active" again. 

How to deactivate/activate a video/audio file

In your Lightcast Media Cloud account go to "Media" in the left-hand menu and select either "Video Archive" or "Audio Archive". Then search for the video or audio file you would like to activate/deactivate. 

If the status of the video or audio content is "active" and you would like to change it to "inactive", simply click on the status "active". This will turn it into "inactive". 

If you would like to turn the video or audio content to "active" again, click on the status "inactive". This will turn it into "active" again.