This Is Mine Achievement in Dishonored
This Is Mine10
You recovered your belongings
How to unlock This Is Mine
Mission 7: The Flooded District
In mission 7 when you lose your equipment, a marker will pop up at the beginning of the level showing you where it is. It's a bit out of the way, and possibly unnecessary if you won't be killing anyone anyway, so depending on your run you can skip it if you want and do it on a High Chaos level playthrough. Just remember, it has your Sleep Bolts! Follow the marker and eventually you'll reach the equipment at the bottom of a weeper filled building.