Find the Key in East Longfall Wetland

Journal
I still haven't found Vivienne's missing vault key, but I did return the key I found to it's owner, James Cook. Coincidentally, he found a different key the night before, and traded it for a drink to an elf named Premislaus. The elf once lived in Aerie, but moved to East Longfall Wetland after his realty business failed. I need to find the bank key either on Premislaus or his property.