You are probably right about that. I think a ground search by the public in the early days certainly wouldn't have hurt the investigation. I mean, in situations such as these, people really, really want to help and this would have been a good way to allow that to happen.
As a sidenote, I had a dream the other night that they found NG alive and she was being hidden in the desert in an underground tunnel / cave. This means I'm either a visionary, or I'm consuming too much social media on this case!