SAN FRANCISCO – More than two weeks after they were first spotted far up the Sacramento River, two lost humpback whales appeared to have finally found their way home Wednesday.

Officials said they assumed the pair returned to the open sea, undoing a wrong turn that drew thousands of admirers and a flurry of rescue efforts.

The unpredictable duo, believed to be a mother and calf, were last seen at sunset Tuesday less than 10 miles from the Golden Gate Bridge, after they traveled 25 miles southwest from another busy bridge. The convoy of boats that accompanied them across the bay to keep traffic at a distance abandoned their escort service when it got dark.

Officials believe the whales slipped out of San Francisco Bay to the open sea late Tuesday night or early Wednesday morning, when no one was watching.

“If they have gone out and made their way past the Golden Gate, they have done so quietly,” said Bernadette Fees, deputy director of the California Department of Fish and Game.

To make sure the whales didn’t take another wrong turn, two government boats were launched Wednesday to look for them in the Pacific Ocean, Fees said.

As the afternoon wore on and only a false sighting of two gray whales was produced, officials grew increasingly confident that the humpbacks, which were injured by a boat during their two-week sojourn inland, were on the move and made plans to stop searching for them.

“If we don’t see them, we are going to call it,” said Jim Oswald, a spokesman for the nonprofit Marine Mammal Center, a private scientific and rescue organization.

Marine scientists said Wednesday that although they will never know why the pair swam 90 miles inland, the massive operation to rescue the humpbacks yielded valuable information about the endangered species. It was the first time the same humpbacks were studied in the wild for so long, according to Fees.