Lina’s case is rare. Most children who are reported missing are eventually found, according to the National Center for Missing & Exploited Children. The few who remain missing are often categorized as runaways and, in some cases, they fall victims of sex trafficking, experts said.

The mystery surrounding Lina’s case has only added another element of turmoil to already traumatized émigrés. Many come to America starting from zero, without a place to live, with limited English skills, if they speak it at all, and few job leads to support their families, said Amir Mohammad Amiri, an Afghan community leader.

“We come here looking for peace, stability, security for our children,” Mr. Amiri said. Now, he is not so sure America is the safe haven he once believed it to be. San Antonio, after all, is an hour and a half away from Uvalde, where 19 children and two teachers were killed in May by a teenage gunman.

News of the girl’s disappearance was all people could talk about at Aryana Halal Meat Market, a gathering spot for many Afghan refugees. Aminullah Amir, 38, stood next to the cashier and tried to explain that he has become paranoid every time he takes his children ages 2, 4, 6 and 9 to the park. “I keep my eyes on them all the time. I am scared that they will disappear like Lina,” Mr. Amir said. “We always thought America was safe. Now, we are not too sure.”

There was a time when the future looked a lot brighter for the Sardars. They tried their best to acclimate to their new life in San Antonio, a Latino majority metropolitan area where hundreds of Afghan refugees resettled after the fall of Kabul, bringing the total population to more than 2,660, according to some estimates. Mr. Sardar soon found work as a truck driver, and Ms. Sardar made friends with close-knit Afghan women in her complex and with neighbors of diverse ethnicities. Their son Rayhan was born in San Antonio.