Storm Coast Red Templar Key

I'm at the Storm Coast, Daerwin's Mouth and there is a room that requires the "Red Templar Key" to open.

I've completed the entire area and was unable to obtain the key.

I searched the web and apparently it's supposed to be looted from a corpse by these two boats near the entrance.

I remember I looted the corpse but apparently did not get the key.

Someone suggested to restart at the nearest camp and go back to the area, which I did, and still nothing else to loot.

Another person suggested to jump of  a ledge behind the room and while the main character is stuck,

the party members will appear to be inside the room and just switching to them as the controlled character would enable me to complete the area.

I tried jumping off the ledge but could not find the right spot to get the party members to appear inside the room.

Please help!