Problem with orphan bsp "brushes"

I used the first person starter as a basis for testing some asset imports. As I imported various assets I decided to increase the size of the level. I selected the walls and moved them further apart.

I proceeded to import a bunch of assets, but now that I don’t need the walls I go to delete them only to find I cant. They are being rendered, you can select a face of them as though you are in face edit mode, but no gizmo shows up and they can’t actually be edited. Whats even weirder is that in the details pane, I get the BSP and Surface Properties panels, but not the Brush Settings panel. Which makes me think that somehow the BSP has become orphaned.

The object doesn’t appear in the outliner either, pressing delete while a face of the thing is selected gives an error that it can’t find the actor.

Is there any way to force a refresh? I suspect its some ref counting issue leaving an orphan mesh of some description, but a file save and load doesn’t help there.

If need be I’ll just nuke the level and start again, but it’d be a pain to have to do that if I were working on a real project.

Is there any way to force a purge of orphaned objects that aren’t in the scene?

Turns out the brushes were there, just disabled by not having the eye icon clicked in the scene outliner. Very weird, but hey it wasn’t a bug!