Obviously local conditions have a lot to do with it, but the majority of planted pine tracts around here, in my experience, will have an opening or two somewhere within them. Usually it's a spot that tends to be wet. Could be it was too wet when they were planting or simply too wet to sustain the pines after planting and they died. Regardless, it's worth a serious look via google earth. It's a whole lot easier than stumbling around in a thicket hoping to find a spot.