Here is what I hear on the HT video (a better mic would have helped a lot, HT):
Mr. Spierer in response to a question about students coming back, says (1:10-1:31 on video): "Well, obviously, the first message is that Lauren or a [Mrs. Spierer interjects "friend"] and co-student is still missing and we need your help to find her. Any piece of information, however small, we need that help."
Then Mrs. Spierer talks about any rumor, anything having to do with Lauren, could be the piece of the puzzle that leads to finding her.
Then Mr. Spierer says: "Lauren's disappearance is puzzling but we know that someone knows the facts around her disappearance and that's what's so terribly frustrating and heart-wrenching for us and everyone that knows her. We can't get that one person to find the courage to come forward."
(emphasis mine)
So, from this, I believe Mr. Spierer was referring to Lauren at the 1:10 mark, not one of the POI's, and Mrs. Spierer is trying to help him find the word that encompasses who Lauren is to students. Maybe she uses the word "friend" to target the POI's, I don't know, but it doesn't sound like it to me.
The second part of the quote indicates that the Spierers and LE must believe that ONE person knows and that person will not tell them anything. All this time, all this heartache, when SOMEONE knows. How incredibly frustrating and maddening that would be. Those poor people.
And, a little off topic, don't you think Lauren looks a lot like her mom?
The Spierers are incredibly strong people.
And one more thing, the second quote above indicates that all the POI's don't know, just one. And it seems that LE and the Spierers know who the person who knows is. (How's that for good sentence structure?!)