Her father, Josh Evans, told Fox11 that Evie was hit in the middle of her forehead while on the steel roller coaster.
It was only when the ride came to a stop that Evie was able to call out for help. Another rider told the family it was a cell phone, Mr Evans said.
Those riders, who were seated behind Evie and her mother, had apparently seen the cell phone flying out of someone’s hand mid-ride.
Mr Evans said when his daughter removed her hand from her eye and forehead, there was blood everywhere. She was taken to a medical aid centre at the park for immediate treatment.
“It was really scary,” said Evie to NBC Los Angeles. “I was screaming and crying.”
Evie’s sister said a man came up to the family looking for his cell phone when the ride had ended, and that upon learning of the eight-year-old’s injuries said the Evans should “stop freaking out”.
The man allegedly added that it wasn’t “a big deal,” the sister added to NBC.
Mr Evans is now calling for the man to come forward to help pay for his daughter’s medical expenses, having been told by local police that no crime was committed.
“You are not supposed to leave,” he said. “I thought it was illegal, just like a hit-and-run.”
Mr Evans added to Fox11 that he was unsatisfied with the park’s response because somebody was at fault for what happened.
“I guess it was a friendly way to say that they are not taking responsibility for what happened,” he said of a Six Flag’s statement. “So, who is at fault here?”
The park told news outlets that it had already responded to Mr Evans’ requests for information on the cell phone owner and that the park has a policy banning loose articles on rides.
In a statement to The Independent, a spokesperson for Six Flags said: “Our ride safety policy strictly prohibits all loose articles on rides. Safety is a partnership between our guests and the park, and guests must follow all written and verbal instructions for safe riding. Our park safety team has already responded to this guest’s request for information.”