After the deadly and fast-growing wildfire began to threaten his hometown, Paradise, Calif., on Thursday, Al Silva got in his four-door Buick sedan and fled west.

His family made contact with the 91-year-old on Thursday night, when he was at a parking lot in Chico, Calif., Mari Irby, Mr. Silva’s great-niece, said.

And then, silence.

For nearly two days, Mr. Silva’s family called shelters, hospitals and filed a missing persons report with the police, Ms. Irby said. She posted a plea on Twitter for help. She said Mr. Silva had left his cellphone in his home, which was almost certainly destroyed.

“What everybody is trying to figure out is: Would he have gone back to try to get stuff? Did he realize he left his cellphone and went to go get it?” Ms. Irby said on Saturday.