Wisp chest in cascades

I'm trying to find the wisp that goes to a chest in the cascades of necropolis hall. I looked online and it seems like it ought to be found at a particular door, but nothing I do allows me to use Emmrich's skill to find the wisp.

Is this actually where the wisp should be? Is there anything I can do to make it show up? I've tried with and without Emmrich in my party.