(CNN) -- Friends and family of Sandra Coke, a 50-year-old woman missing from Oakland, California, begged the public for information Thursday that might help bring her home.
Coke was last seen Sunday. She left home to get something for her 15-year-old daughter from the drugstore, according to Coke's longtime friend Wendy Springer.
"Hours later when she didn't come back, her daughter called me -- frightened. And that is too unusual. She never would have left her daughter for more than 15 minutes and not checked in," Springer told reporters Thursday.
She spoke alongside Coke's sister, Tanya Coke. They announced a $100,000 reward.
"We all are just desperate to see her returned home safely, and so we are again asking anybody with information about my sister -- Sandra Coke -- to please please come forward," Tanya Coke said.
Sandra Coke was last seen wearing a black and white shirt and dark jeans. She is African American, 5 feet 6 inches tall, about 150 pounds and has brown hair and brown eyes.
According to Oakland police, she is in good mental and physical health, with no history of being reported missing.
Her vehicle, a 2007 Mini Cooper convertible, was found in a parking lot Monday.
Police have said they are chasing leads, while friends and family are canvassing neighborhoods. Tanya Coke showed reporters a flier that she and others were planning to post around the city. The reward was featured prominently.
Sandra Coke works as an investigator for a federal public defender's office.
But Springer, who has known Coke since they were children, said she doesn't think her friend's disappearance is connected to her job.
"If there were something that was going on, I think I would have known about it," she said.
Anyone with information about Coke is being urged to contact the Oakland Police Department Missing Persons Section at 510-238-3641.