In Nine's Legacy, Sandor gets caught by the Mogs, and they torture him to get information out of Nine. But how did they know that he was Nine's Cepan? They caught him because he was "poking around" at the They Walk Among Us magazine, but he could have been any of the Cepans.
I think because
- Cepan of number 1, 2, 3 killed along with the Garde
- Cepan of number 6 die too
- Cepan of number 8 die in India
- Cepan of number 5 already dead when they found him
=> They know for sure 6 Cepan of which number have die so when they find Sandor, they though him either Cepan of 4 or 7 or 9, and since the Cepan not go around carry the chest without his/her Garde the Mog can assume he is 9's Cepan
Beside, all Loric Chest have Loric symbol on it (can't confirm if it contain number of each Garde or not) so it maybe a good lead