The detail that best supports Frankie’s thesis statement is:
"Soon, he, too, was filled with a new determination; Storey borrowed money from friends, dug out some old type from his barn, and had the Times publishing again on October 18."
This detail illustrates the collective effort and determination of individuals, specifically a business owner (Storey), to restore the city after the fire by resuming publication of the newspaper, which is a crucial aspect of the city's recovery.