Police and family members spent hours hunting for Amieya Renee Stewart, 4, Friday night, KNBC-TV, Los Angeles, reported.
"She was surrounded by many different items and unfortunately had gone undetected," Lt. Bisa French said.
The girl had disappeared shortly before 5 p.m. during a family gathering and wasn't found until nearly midnight, the TV station said. Even police dogs had missed her.
Her grandmother told KNTV-TV, San Francisco, Amieya likes to hide. The girl's mother told reporters she was sorry to have caused people to worry.