We all understand what this message means and why S1 can't really help us with that. But sometimes this is simply because the vendor has renamed the plugin, or there is a new version, that replaced an older one.
How about asking S1 to point to a replacement or newer version of the plugin? It could just be a "Locate" button in the "Missing Plugin" dialogue, that allows the user to manually point to a new version or an alternative.
S1 could then also ask "Update all instances?", because oftentimes we have many instances of a plugin scattered around the project.