The line comes from the SCP universe, where Mobile Task Force units are sent to recapture escaped anomalies after a containment breach. In SCP games the radio updates are kept short and formal, so a lost target is reported the same way as an enemy spotted callout in a shooter. Players began clipping the announcement for edits and streams outside the games, using it whenever a chase, search or plan fails in a funny way, and it remains a staple sound for SCP gameplay content.