Has anyone found it ? I've scouted the area mentionned on the map for at least 30 min now, but never have I been able to find it.

You talking about the one in the Pass of Woes? It should just happen randomly. It probably requires a survival skill of a certain level to find it though (and I have no idea what that minimum level could be - I've found it in practically every play through).

Did you activate the supporter pack DLC in configuration?

The spot is pretty much left to the middle, south of the Factory and to the east of the Drunken Lair.

Okay, I actually had to reinstall the game, because it wouldn't update itself to the latest patch and supporter pack. Resolved now.