Phantom traffic jams—stop-and-go waves emerging without visible bottlenecks—are often described as “causeless” anomalies in dense traffic flow. While existing density-wave models successfully explain how such waves form through instability amplification and delayed feedback, they leave a persistence gap: why congestion patterns remain after the initiating disturbance has vanished and no new trigger is observable. This paper reframes phantom traffic jams as an observable phenotype of Dark Phase Memory (ΦDark)—a post-threshold phase regime in which coherence is preserved while reversibility, interpretability, and navigability are structurally exhausted. Rather than treating phantom jams as dynamically sustained responses to present conditions, the ΦDark framework interprets persistence as structural: a consequence of path deletion caused by accumulated historical phase mismatch. We introduce an operational notion of ghostification in self-driven flows, formalizing how microscopic deceleration events integrate via reaction delay (τ), cross a recoverability threshold (CRGZ exit), and invert into a residual phase regime. The defining observational signature is anti-phase propagation, in which agents move forward while the constraint pattern propagates backward, revealing a sign conflict between intention and structure. To establish generality, the paper advances a scale-bridging principle, demonstrating that phantom traffic jams and galactic spiral arms are not metaphorically similar but structurally isomorphic density-wave systems. In both cases, particles traverse a long-lived pattern that persists independently of its constituents, expressing ΦDark as activated history rather than ongoing forcing. Beyond traffic systems, this work positions phantom jams as the first empirically accessible entry in a broader ΦDark phenotype map, offering diagnostic criteria for identifying residual constraint regimes across physical, social, and organizational systems. The paper concludes by previewing connections to the Hourglass structure and Joint Alignment Memory (JAM), framing phantom traffic jams as a real-time, observable throat-dynamics case where outer order coexists with inner navigational collapse. This work is an exploratory contribution situated within the IPCSALT–UPF phase-based meta-framework.