I have been reading Sean Munger's blog, and he periodically posts about missing persons. There was one he did because the missing person came from the same area he did. There is next to no info on the case. He was travelling with a friend, and the 2 guys had an argument. Jay, missing person, got out of the car and wasn't seen again. The few details in the case don't make it clear if the argument was in a small town in California or Las Vegas, and there was no follow up with friend to clarify.
The case is 40 years old, and Munger said that the lack of details is so unsettling. There is no mention of Jay's family in the case file. Did he have no family, or did they not care? Or did they try, but police resources were so limited back then that after a preliminary effort they were discouraged? Munger did point out that in missing person's cases, having an active family presence pushing and pushing and wanting answers seems to help a lot.
I think that is what unsettles me about missing persons cases: no one will know what happened to you, and sometimes, no one seems to care.