I don't think we know that is the case:
From Wed-
The 84-year-old was reported missing on Sunday after missing church.
www.yahoo.com
Then 2 hrs ago
TUCSON (KVOA) - As the search for Nancy Guthrie enters its second week, law enforcement activity continues around her family's residences. Police were observed at the home of Annie Guthrie,
www.kvoa.com
Savannah Guthrie and her siblings, who had been staying at their older sister's home several miles away, left the location as investigators conducted their search.
So they were there for the search, but this also confirms it was a search.
This is most confusing case I have ever followed.