Her brother said he would search La Tourette meaning thinks she is buried there? The golf course itself is maintained all the time so what are the chances a body might have been discovered? (imo) But there are woods all around.
Was La Tourette a known hang out spot among SI kids? Was it fenced in in the 70’s? -Easy road access? It was the kids who grew up in my hometown who knew about and visited the golf course.
I think it could be a reference to a known accessible spot that might not have been monitored by LE, like the public places, parklands with closing hours after dark?
It also suggests someone would know that terrain well to hide a body there. –all imo.
ETA: Don't know if there is a more specific reason to suggest a search of La Tourette, only that it came from someone close who's had much time to perhaps search himself, and to think about where and why...