I'm at 17/18 for the triumph. The info broker tells me it's on Hellas Fortitudre (i'm assuming Totality, by his wording) but I've collected all three ghosts from there. (Ran through on all characters/factions, no deposit placement found in tharsis, and no ghosts in the HF locations. Double checked each spot during Contested location day for HF) The missing placement seems to be the bookcase by the entrance of the ghosts' playhouse.