This paper presents a minimal formal extension of the Domain of Non-Existence framework. The original framework treats N(t) — the set of non-observable states — as a unified category. Drawing on a physical resonance box experiment and 1D wave simulation, this paper demonstrates that N(t) has internal structure: at least two distinct mechanisms produce non-observable states, each requiring different interventions. Type I (Constraint-Blocked): the constraint structure C structurally forbids the state. Type II (Dynamics-Blocked): C permits the state, but system dynamics Φ cannot reach it from the current operating point. The paper introduces the Constraint-Accessibility Mapping operator E_obs = M(C, Φ) and formally decomposes N(t) = N_C(t) ∪ N_Φ(t). A third mechanism, Type III (Observation-Blocked), is identified as future work.