Augusta National spokesman Steve Ethun said the guard acted improperly in stopping Sullivan, because club policy is to provide equal access to all reporters. The club has no female members, but several female reporters at the tournament confirmed they had made numerous trips to the locker room for interviews in the past without incident.
Sullivan was among a crowd of reporters following third-round leader Rory McIlroy from the course into the clubhouse after his collapse in the final round.
"She just said women were not allowed and there was no official in sight," Sullivan said. By the time Sullivan finished trying to locate McIlroy's manager, the interview had been completed.
Ethun said the club hires a number of people to work the tournament and the guard was apparently unaware of the equal-access policy.
"It should not have happened," he said. "We will work as hard as we can to make sure it does not happen again."