Rex Salazar's journal is an object in which Rex records important memories or information just in case of a "blackout", in which he can lose all his memories.
Rex's first journal was a personal digital assistant (PDA) that he kept during his earlier teenage years living with his old gang in Hong Kong. The journal was first mentioned by Tuck during their reunion after Rex joined Providence.
Tuck said that Rex always kept the mobile device uploaded with everything he found important in case he'd blank out. The journal's purpose was to record everything Rex is or at least what he used to be. When Rex decided to abandon his friends, he left the journal in Quarry's possession.
As Quarry and Rex met again years later, the crime lord presented the journal and revealed Rex's dark past: he used to be his top lieutenant. Quarry strengthened his revelation with Rex's recorded voice as proof. In the end, Rex destroyed the journal. Thus, he sacrificed the only clue to retrieving his past in order to liberate his friends from Quarry.
The second journal was given by Agent Six, in response to Rex's fear of losing his memory. It was given after he and Dr. Holiday heard his story after he was done doing an undercover mission in Hong Kong. Unlike the first journal, which was a digital device, the second one was an ordinary brown notebook.
- Apart from writing, Rex also uses photos to "remember" certain events of his life.