The only reason LE hunker down like this is when they are running an active investigation with firm POI's.
Otherwise they go public to ask for help.
LE have asked for help in the early days but silence since.
This implies to me at least, they got that help.
There is a world of difference between having a POI and an excellent idea of what happened, and proving it without reasonable doubt in a courtroom.
I suggest the silence is because they are working the case.
In Daniel Morcombe's case it took 8 years, a coronial inquiry, and a undercover operation before an arrest was made, even though the perp was located in the first fortnight.
It takes time.
Have a read of how many "unsolved" murder cases have a POI wandering around, just because LE can't prove their theory to the level it requires to make a successful conviction.
Casey Anthony and OJ and John and Patsy Ramsey are examples of what can happen when a case is laid without enough hard evidence to prove beyond reasonable doubt.
<respectfully BBM for Focus>
http://wcfcourier.com/news/evansdal...cle_bc5363a2-dcf1-11e2-be6a-001a4bcf887a.html
New and old tips led to new appeal in abducted cousins case, chief says
June 25, 2013
EVANSDALE, Iowa --- A combination of new and old information prompted law enforcement Monday to renew a request for the publics help in the ongoing investigation of the disappearance and deaths of cousins Lyric Cook-Morrissey and Elizabeth Collins.