Authorities said the girl and her two siblings were home alone sleeping in their apartment on Herman Drive and Pike Street on Saturday night when the kidnapper entered through an unlocked window and snatched the girl from her bed.
The girl was dropped off some time before 1 a.m. Sunday in a neighborhood a few miles away at Giles Court and Bolton Avenue, where residents said she seemed disoriented.
"I heard somebody knocking on my door, and I thought it was somebody that was drunk or something," said resident Celia Diaz, who called police. "She didn't have any shoes, just a little T-shirt and shorts."
Diaz said the girl was asking to be let inside, saying she was really cold. The girl knocked on at least two other doors for help.
Authorities said the girl was hospitalized at Loma Linda University Medical Center in serious condition, with injuries suffered during the abduction. It's unclear if she was sexually assaulted by her kidnapper.
"It's very disturbing," said neighbor Sabrina Lopez. "There are so many kids running around all the time."
Robert Zablockis said his son lives in the apartment complex, but didn't hear anything.
"The people who woke him up were the detectives," Zablockis said. "He goes, 'There's a bunch of people out here, a crime scene van and a bunch of cops. The girl next door got kidnapped and beat up.'"
Not much is known about the child's mother. Neighbors said she is about 30 years old and works at a local bar.
Anyone with information on the abduction is urged to contact Riverside police at (951) 353-7124.