Just to answer the first sentence, the FBI were involved in the search of the Rexburgh apartments. Below is the link.
Missing Idaho kids: Police asked for school records in relation to 'homicide' investigation
(FBI were also involved in the search at the Salem property too.)
I stand corrected. I'd seen reports saying the FBI was involved in the search of Chad's house, but that's the first time I'd seen something saying they were also involved in searching Lori's. And I'll note this is talking about a search in December which I'd also not heard about. I was thinking Lori's house was only searched on November 27th. Thanks for the correction.