Boy this case is really a puzzle. I wonder if Nancy made it a habit to take a day alone to drive down the coast...find a spot by the cliffs just to relax and read? That sounds like something that I would love to do. But I wonder if it is something that she had done before?
The oriental man that she had lunch with might not have been a man that she was with but maybe someone that she ran into that she knew through the school where she was an administrater. She probably knew a lot of people through her work. Maybe they were both alone and just decided to eat together instead of alone. If people there knew who she was then someone must have noticed how the two people interacted with each other.
You can watch a couple just a little and get an idea if they have something going on or not. Body language speaks real loud. Sounds like he was a lot younger then her.
You would think if she was going to take off with someone she would have taken her wallet instead of leaving it locked in the van. Sounds like her chair, book and hat were right where she left them.....like there wasn't a fight with someone. If she had gone off a cliff she would have been found by LE. Sounds like she either went willingly with someone or was grabbed and taken.
But why would she have left her husband, kids, and grandbaby without even a hint of there being something wrong?