Her suspected kidnapper, West Wild Hogs, is in custody, the TBI said.
Hogs was captured after an employee of Baptist Memorial Hospital in Memphis, Tennessee, called security to say Hogs was at the hospital, Memphis Police Department spokeswoman Lt. Karen Rudolph told reporters. She did not know why Hogs visited the medical center, she said.
Police pulled over Hogs in the hospital's parking lot, she said. Hogs was arrested without incident.
"It doesn't seem that she has any apparent injuries," but paramedics are examining her to be sure, Rudolph said.
Earlier, Polk County Sheriff Grady Judd held a news conference in Florida in which he warned that Hogs was a truck driver by trade and feels "very comfortable on highways. He was seen in Nashville around 2:30 a.m. Monday, the sheriff said.
His family has told investigators that he suffers from depression and bipolar disorder, said Donna Wood, spokeswoman for the Polk County (Florida) Sheriff's Office.
Though Judd told reporters that Hogs has no criminal history and does not seem violent, he also said Hogs had previously lived with the Lewis family, when Rebecca was an infant, but he pulled a gun on the family "so the mama ran him off."
Did Tennessee drop ball?
It was far from the only bizarre piece of information provided at the Monday news conference. Judd suggested Hogs might already be in custody if Tennessee authorities had issued an Amber Alert earlier.
Late Sunday night, a ranger encountered Hogs and the girl at Cove Lake State Park in Caryville, Tennessee, about 20 miles south of the Kentucky border, Judd said.
Hogs told the ranger he was waiting on Rebecca's mother, the ranger told him the park was closed and Hogs left, the sheriff said. Only later did the ranger see a bulletin and realize that he'd spoken to Hogs, Judd said.
Tennessee declined to issue an Amber Alert, Judd said, because there was no evidence the girl was in Tennessee.
"Here's a news flash, Tennessee: He was there," the sheriff said.
TBI spokesman Josh DeVine told CNN on Monday morning that the bureau would respond, but there were "some potential developments in the case that've taken precedence for the time being."
According to the Justice Department's federal guidelines, Amber Alerts should be issued when authorities have a "reasonable belief" a child younger than 18 has been abducted and is in danger of bodily harm or death.
To issue activations without "significant information" indicating an abduction has occurred would be problematic, the Justice Department says, but "at the same time, each case must be appraised on its own merits and a judgment call made quickly. Law enforcement must understand that a 'best judgment' approach, based on the evidence, is appropriate and necessary."
The ordeal began last week, a few days before the kidnapping, Judd said. Hogs was at his home in Seale, Alabama, on October 3 when he told his wife he had a surprise for her. They got in the car and headed north to Interstate 75, which they drove all the way to Kentucky, Judd said.
From there, they went to West Virginia, then Virginia, then Maryland, where they rested at a welcome center. They then took Interstate 95 South to Charlotte, North Carolina, and drove west to Tennessee, where they took Interstate 75 into south Georgia. It was Thursday by then, and his wife decided to abandon the trip, Judd said. She got out of the car and called relatives to take her back to Seale.
On Friday, Hogs showed up at the Polk City, Florida, home of his grandmother, whom he hasn't seen in a year. He spent the night, and when his grandmother was getting ready to go to work in Clermont, he asked about Rebecca's family, as well as for the addresses of Walmart stores in the area, Judd said.
Around 9:30 a.m. Saturday, Rebecca's 16-year-old sister went to check on her and couldn't find her. Judd said he didn't know exactly how Hogs abducted Rebecca -- namely, whether he took her from the yard or home -- but he apparently kidnapped her before 9:30 a.m. and took her to a McDonald's where they spent about 30 minutes eating breakfast.
Hogs and Rebecca weren't seen again until 6:30 p.m. Saturday when they turned up at a BP gas station off Interstate 75 in Forsyth, Georgia, where Hogs bought drinks, the sheriff said. They were then seen in Caryville, Tennessee, late Sunday and in Nashville a few hours later.
A the time of Hogs' arrest, five states -- Alabama, Florida, Georgia, Kentucky and Tennessee -- had issued Amber Alerts, according to the sheriff's office.