Radio transcripts by the Americans.
Intercepts on open channels from the guides back 'somewhere else'.
The testimony of a spy jailed by the US.
And, most telling, the testimony of your own media. A Pakistani channel sent a team to dig out the survivor's village and parents. They did an interview, and wanted to follow it up the next morning. The family had disappeared; nobody in the village knew about them. Only some large gentlemen in very large black boots were hanging around, wearing their most journalist-friendly faces.