That's not the point. Maybe someone knows her but does not know that she's missing. There may be 100 women out there with that tattoo and 99 of them are fine.
There's no one matching that description in the national missing person database. Women age 20 to 40 just don't go missing very often. In all of 2012, there were no women that age reported missing in CA, and only a handful of cases in all southwestern states (mostly women trying to cross the border illegally.) She could have been a recent immigrant from Mexico without strong ties to LA, and with no one to report her.