Miranda rights attach any time one is in any type of police "custody". What I mean is if it is highly irregular for LE to stay at the home of someone they consider a suspect, and they are there unwelcomed, it could be argued that they should have been mirandized because they questioned them and stayed at their home under the guise of helping when the homeowners did not have a choice if they stayed or not. if that is the case, I would argue that they are in custody as they are not free in the complete sense of the word.Miranda rights only attach during a police interrogation. If the LE present isn't asking questions of a suspect, then would be no problem.
But I personally don't think that they are doing anything irregular as having a police liasion in a high profile missing case is SOP in many cases.