Object in all Layers

Hey all,

I just noticed that my single object is every layer and I don’t know why. I fixed it by moving on of the copies into Layer 1. After moving one, all the others disappeared. It’s fixed but I would like to know what happened.

.blend file: singleWall_001.blend (449 KB)

There’s only one object, it’s set to be on all scene layers. Moving it to one scene layer means it’s only on that layer, but still just one object.

How did I accidentally do this? Is there a hotkey for this and what would be the purpose of doing this?