The FBI is involved in so many cases including those where the parents or family members are not suspects!
When it's an abduction the risks the victim is taken across State Lines are high and that's why they get involved and/or illegal activities in some cases. Once it is established not to be the case, they let local LE handle it going forward.
I realize all of the above.
But these parents had at their disposal an agency who is trained on missing persons cases and who had the ability to help find Lisa. FBI upholds bigger standards then LE does.
From the blog:
However, there are too many law enforcement professionals with too much experience from too many agencies for that to be true. The FBI, who has been involved since the beginning of the investigation has prioritized missing children since 1993. They have a written protocol and agents that are specifically trained in missing child investigations. Given their standing in the law enforcement community and the resource that they bring to bear on missing person cases, it would be counterproductive and reflect badly on the agency to force blame on innocent and suffering parents.
A very good point he made! Especially the last sentence.