The time has long passed, in my humble opinion. Once they reported Brian 'missing'.. it was over. Ovah. ...
Realistically.. once the Laundrie clan closed off the Petito's calls, ( before they started ringing, the fix was in...) they were expecting those calls from the Petito's.. I have no doubts about that ,, they knew Gabby's mum and dad would be ringing, they put in place the process not to answer any of those numbers.
( I have often wondered if the Petito's had used someone else's phone, would they have got a pickup?>. I think they would have. )