I got a treasure map supposedly for the treasure of Baron Decard of Longhorn from the injured werewolf named Kenthwarr who Gerhard the paladin asked me to kill and I can't seem to find the treasure. Where specifically is it in the Schwarzwald? How will I know once I've found it?

I checked some of the hidden treasure containers in the schwarzwald inn area and the Schwarzwald area but nothing about them gave it away although I remember hearing a unique sound when I uncovered one of these.

The treasure can be found in the Schwarzwald Inn area (because the description of the Treasure map from Kenthwarr says "Apparently the treasure is buried in Schwarzwald, near the coaching inn"). When there, open the map - there is a big rock north of the inn. Go to it and inspect a few small boulders to the right of the big rock. There is also a tree just above these boulders near to which a Devil's Root can be found. You can tell you have found the correct container because Baron Decard of Longhorn's Ghost will appear after you open it.