Finding a Scene's Users

A scene in my blend file has suddenly developed two users.

I can’t click to “make single user” on a scene, and I have no idea how this happened - it was certainly not intended - or what else has become a user of this scene. Saving, closing Blender and re-opening doesn’t change it. I’ve also checked with the outliner and the scene does not have a fake user either.

How can I find out what users the scene has, in order to track down what happened? And what sort of objects can be users of a scene anyway? As they’re kind of “top level” objects, so I didn’t even realise that this was even possible.

Thanks in advance.

Ah, right.

Yes, I did play around with creating a RenderLayer, as an experiment, to see if I could pull off a particular effect.

But it didn’t really work as intended, so I deleted it.

The thing is, that RenderLayer is now gone. I’ve saved and reloaded the .blend file and the scene still has a “2” next to it, even though - as it’s not used anywhere - it ought to have been purged.