Just 4.3 pounds and 15 inches long, the infant is now getting treatment in a neonatal intensive care unit at an undisclosed Los Angeles hospital.
"She was cold to the touch (when rescued)" Friday afternoon, Los Angeles County Sheriff Jim McDonnell said Monday. "The baby would not have survived cold temperatures overnight."
The girl -- estimated to be 4 or 5 days old -- may not have been found if not for the sharp ears of two sisters strolling near the riverbed between 136th Street and Slater Avenue.
"I walk along this path every morning," Evangelina McCrary said. "But it was so cold on Friday that my sister and I decided to walk during the afternoon."
The sisters first thought the strange sounds they heard might be from a cat, but instinct told them to call 911 and put the phone near the source of the muffled cries.
The emergency operator instantly dispatched two deputies to the riverbed.
"I could hear the baby crying and crying, but once I looked into the hole, I couldn't see the baby," McCrary said. "All I could see was dirt and rocks."
Adam Collette, a 36-year-old deputy and father of two young girls, arrived and began removing debris.
"(The) cry I heard as a father was more of a cry for help, 'I'm hungry' -- not an 'I'm injured' cry," Collette said at a news conference on Monday.
McCrary said once Collette picked up the baby, "It finally stopped crying."
"I was so relieved, so thankful, I started crying myself," said McCrary, who has five grandchildren.
Social workers said the baby could have been brought to a hospital or fire station under the county's Baby Safe Surrender Program
. Since the program's inception in 2001, 140 babies have been safely surrendered.
"No shame, no blame, no name," Fourth District Supervisor Don Knabe said. "We need the public's help identifying the mother."
The baby, who has a full head of black hair, is possibly Hispanic or African-American, and was wrapped in a hospital blanket, according to Detective Jennifer Valenzuela of the Special Victims Bureau.
Valenzuela urged the baby's mother to come forward, emphasizing she could be a mother in trouble, and that there may be no criminal charges.
"We're concerned for her well-being," Valenzuela said. "We don't know if there's mental illness or she's a young mother."
If the mother isn't found, or can't care for the child, or doesn't want to, the baby will go into foster care.
The sheriff counted blessings when reflecting on how the story of the little girl could have ended. The girl is only the 14th of 67 abandoned babies found in the county since 2001 to have lived, according to authorities.
"Sadly, innocent children forever lost because of shame, confusion, and fear of parents unable to raise child," McDonnell said. "In this case, we're extremely lucky."
"To wake up in a dark hole, if the baby wasn't crying when she did, she probably would not have been found," Collette said.
And McCrary, who with her sister decided to take a later walk on Friday, can't stop thinking about what might have been.
"I'm so thankful God sent me on that path," she said. "I've been to the spot since this happened and I pray that this doesn't happen ever again."