This essay proposes the “Erased Museum” as both a critical framework and an institutional ethics: a museum that recognizes loss as its primary collection and disappearance as a mode of curation. Drawing from Absential Aesthetics, it argues that destruction—by fire, flood, war, neglect, theft, or obsolescence—does not terminate cultural meaning but reorganizes it into a second, invisible archive composed of voids, residues, and public conscience. Through case studies and touchstones including the Library of Alexandria, Brazil’s National Museum (2018), the Mosul Museum (2015), and architectural and curatorial practices that preserve wounds rather than conceal them (e.g., post-damage restorations and void-centered memorial architectures), the essay reframes conservation as a dialogue with entropy rather than a fantasy of permanence. It also traces contemporary artistic strategies that curate absence directly—fabricated archives, missing inventories, empty frames, restitution bureaucracies—showing how loss can become documentation rather than mere lament. The work concludes by extending the ethics of disappearance to the digital domain, where decay occurs without smoke, and by proposing “transparent loss protocols” as a future-facing curatorial responsibility.