The good ol Cell Phone Waiting Lot. I've been picked up a few times at LAX and my ride could never find it. On a totally unrelated visit, I finally located it. It blends in with Economy Lot C really well, and IIRC, it's just a turnaround with a few parking spots.
In the map above, it's at 96th and Vicksburg where the green, blue and red lines meet.