This enemy only spawns at night.

The Rustling Goblins that roam around the towns at night will have a set path they follow and will then stop and start to loot. Once they complete the action they will despawn and respawn as a Thieving Goblin Rustler. At that point you can then kill them to roll loot on that table.

You must wait for them to walk to a position and loot before you can kill them.

Killing them before they have the 'Thieving' title does not roll from the loot table.