"Anybody know something about this please come forward to represent my baby girl," said Pamela Brown.
Brown believes her daughter left home Sunday night to be with several boys. A farmworker found Stevona's body Monday morning.
She was wrapped in a rug and dumped in a ditch beside an onion field, just east of Palmdale.
The cause of death has yet to be determined.
And that car wash will be held at Cactus Middle School, from 8 a.m. until 4 p.m.