The buried chests are stat checks, not patron items. Dunno where you are in the game's narrative, so I can't direct you much, but I would be surprised at this point if there's an issue with progression in the public build.
After sleeping in the White Rat and talking with Marlan, you have to visit the tents in the mining district to find Ralph, then return to Marlan in the inn.
Mercy won't fight the guy in the aqueducts until after she's encountered the Crows, so if you haven't done that yet, it means you probably haven't progressed to nightfall.