A university student disrupted three THSRC train services for approximately one hour using commodity software-defined radio equipment by exploiting unauthenticated RF-based signaling protocols in legacy rail OT infrastructure, including a system with cryptographic keys unchanged for 19 years. No CVE applies; the vulnerability is an architectural protocol-level flaw in unauthenticated RF signaling systems. This incident establishes that the barrier to entry for physical-layer OT disruption in transportation infrastructure is now commodity hardware ($50 USD) and technical knowledge, with no requirement for network access, insider access, or nation-state resources.