As long as someone remembers, it doesn't matter if it's been "erased" or not. They still exist.

[ Take it from... the amnesiac!!!!! ]

The stars still exist. So does color. [ ... ] So does my home, across the sea. They're all still there, so it makes sense to me why... they still would be. The world hasn't forgotten them, even if you erased them.

[ A wiggle. ]

That's why their faces and names showed up in the basin.