Yeah, that was me who added it. The strangest part is that the legendary pronghorn (which is also mentioned in that quote) is in fact real, but the Mexican trapper himself never appears in New Austin. It's quite sad, this could've livened up a rather empty region.
@Fledcoolguy Update: The Trapper also says “If you meet a falconer up in Roanoke named Jerry, say hi to him for me.” And yet, I can’t seem to find a man like that anywhere in Roanoke Rodge.
