HUNTINGTON BEACH, Calif. — No recoverable oil remains in the water after a sheen was reported off the Southern California coast, but the cause remains unclear, officials said Saturday.Authorities detected the 2.5-mile (4-kilometer) long oil sheen Friday morning. Crews recovered about 85% of it, roughly 85 gallons (322 liters), on Friday.By the time responders conducted flights over the area Saturday, they could no longer see any recoverable sheen, the Coast Guard and Huntington Beach…