Can’t say any of this worked for me unfortunately. It’s so easy to accidentally do it too.
I’d been having issues with an FBX scene that I imported from Blender because the scaling was off, so I deleted the actor from the map (because this is not the first time I’ve had a level with unloaded actors), then deleted the assets, and re-imported the scene from Blender into the content drawer. I opened up some of the scene items in the item editor, and the scale was still off - so I deleted them from the content drawer again.
But UE5 was so nice to have added the scene to the map for me when I imported them.
Another unloaded actor.
Pinning and un-pinning, re-importing the same FBX, nothing works. Luckily I was at a point where I could lose all progress I’d made, so I closed Unreal and didn’t save the project - reopened the project, actors were loaded up, deleted them properly and re-imported the correct scaled ones.