Shortly after leaving the fourth part of the screening, Vicente met the Sovereign, who was in charge of this shift.
He had already removed all the items from his body that could change his appearance, be it his face, biometrics, voice, or aura.
The Sovereign could easily detect all of the artifacts responsible for these disguises, so he had already stored everything in a spatial ring when Torne told him to do so quickly.
No one had noticed him making his changes. Since the soldiers working on the triage would leave this prison at dusk, the only ones who could really find something wrong with Vicente or Sarah's appearance would be them and Evan.
Even if some newly arrived soldier had seen them earlier, it wouldn't caused them any problems. With so many newly arrived soldiers, one could simply think they were among the many people who hadn't noticed them earlier.