Urgent Evidence narrative's node `kb:file2-uuid-1` needs a detection mechanism

This Issue is an anchoring Issue for working towards resolving [this TODO](https://github.com/casework/casework.github.io/blob/7b0f0649c5f0a402fcb0825e9eb6c65f03c6fbc0/examples/urgent_evidence/urgent_evidence.json#L1590).