Media reports said a SLED SUV the governor drove that night was spotted in the airport's parking lot.
Sanford's spokesman Joel Sawyer declined to immediately comment, and the governor did not return cell phone messages.
Critics slammed his administration for lying to the public.
"Lies. Lies. Lies. That's all we get from his staff. That's all we get from his people. That's all we get from him," said state Sen. Jake Knotts, R-West Columbia. "Why all the big cover-up?"
Trying to drive along the coast could frustrate a weekend visitor to Argentina. In Buenos Aires, the Avenida Costanera is the only coastal road, and it's less than two miles long. Reaching coastal resorts to the south requires a drive of nearly four hours on an inland highway with views of endless cattle ranches. To the north is a river delta of islands reached only by boat.
A spokesman for Argentina's immigration agency wouldn't comment Wednesday on whether Sanford entered the country, citing privacy laws.
The governor said he cut his trip short after his chief of staff, Scott English, told him his trip was gaining a lot of media attention and he needed to come back.
When asked why his staff said he was on the Appalachian Trail, Sanford replied, "I don't know."
Sanford later said "in fairness to his staff," he had told them he might go hiking on the Appalachian Trial.
Sanford said he decided not to return via the Columbia airport to avoid the media. The State Media Company was the only media who greeted Sanford this morning.
"I don't know how this thing got blown out of proportion," Sanford said.
Sanford said he has taken adventure trips for years to unwind. He has visited such places as the coast of Turkey, the Greek Isles and South America. He was with friends sometimes and sometimes by himself.
"I would get out of the bubble I am in," Sanford said.
Sanford said the legislative session was a difficult one for him, particularly losing the fight over whether he should accept stimulus $700 million in stimulus money he wanted lawmakers to spend on debt instead of urgent budget needs.
"It was a long session and I needed a break," Sanford said.
After a brief conversation with a reporter, Sanford was escorted away by an aide.
McClatchy Special Correspondent Angeles Mase contributed from Buenos Aires.