There was no warrant. The Court's full opinion is here.
The U.S. Supreme Court has held that an "administrative search" of a regulated business does not require a warrant. Therefore, the court held, the Florida Department of Business Regulation can send an inspector into a barbershop during business hours and ask everyone cutting hair to show them his barber's license. But that exception, the court went on to hold, does not authorize the Police to go into the barbershop with guns drawn and to handcuff everyone present.
Thanks for the link.