Lucero Sarabia, known as “Princess” to her loved ones, was celebrating Thanksgiving 2004 the way the holiday was meant to be celebrated: surrounded by friends and family, enjoying food, laughter and relaxation. The next day, she disappeared. Fifteen years later, her mother and sister are still searching for answers.

Lucero was eight months pregnant with her third child at the time of her disappearance. She and her two young sons lived with her mother Juanita Trevino, and her younger sister Amanda Martinez, in San Antonio, Texas. Juanita told Dateline her daughter had recently separated from her husband of five years, but the 21-year-old was excited for what the future would bring to her growing family.

“She always thought about everybody, and tried to make everybody else happy before making herself happy,” Juanita said. Lucero “gave a lot, and trusted a lot” in other people, which led to some trepidation for her mother.

But, Juanita explained, “we always kept in touch with each other, no matter what we doing,” often calling each other seven to ten times a day.

On that Thanksgiving Day in 2004, Lucero was excited to make Thanksgiving dinner for her family for the first time, celebrating with Juanita, her sons and the rest of her family. A few hours after dinner, her sister Amanda called Lucero to invite her over to her boyfriend’s family dinner; Lucero went over after dropping her mother off at her second job.

Lucero picked up her mother back up from work at 10 p.m. that night, but said she wanted to go back to the party. Juanita said she then dropped her daughter off at the party and went home. She asked Lucero to call her when she was ready to go home.

“After that, I don’t know what happened – I know my daughter didn’t make it home,” Juanita told Dateline.

Juanita said she spoke to Lucero at 1:30 in the morning, telling her it was getting late. Juanita said she then heard Lucero ask another guest at the party to give her a ride home. When Juanita woke up just a few hours later for her 7 a.m. shift, Lucero still wasn’t home.

Since she had to work, Juanita asked her daughter Amanda to keep calling Lucero, to try to find where she was. Hours later, at 11 a.m., neither woman had heard from Lucero, Juanita instinctively knew something was wrong.

Juanita went to the police, who she said told her they couldn’t do anything until Lucero had been missing for 48 hours.

Dateline reached out to the San Antonio Police Department and Senior Public Information Officer Jennifer S. Rodriguez stated, “This case remains an active missing persons case. We encourage anyone with any information to please contact our Missing Persons Unit at 210-207-7660.”

Juanita is frustrated by what she feels is a lack of attention to her daughter’s disappearance. “She’s become a cold case – where this police department has gotten so many tips for what might have happened to her, but they have not done anything,” Juanita said. “And here we are 15 years later, and nothing has really developed.”

Amanda Martinez, who was 16 when her sister disappeared, says Lucero had a “big heart” and “always wanted to help others,” which makes the lack of resolution even more difficult.

She shares her mother’s frustration. “I can’t say that [the SAPD] really did everything they could for my sister’s case,” Amanda said. “Even now, we reach out to them with tips, and I don’t feel like they’re doing anything, which really bothers me.”

Robert Price of NBC affiliate News 4 San Antonio reported on the case last year, and continues to search for answers for Juanita and Amanda.

“This family unfortunately has to be reminded of this every year, on a holiday about family, and a time for family to come together and celebrate what they’re thankful for,” he said. “They’re reminded of it in a very vivid way every year.”

With all the advancements of the last 15 years, including podcasts, blogs, and social media, Price believes that reaching an audience of citizen sleuths can only help in cases like Lucero’s.

Amanda agrees, saying that the family hopes to reach people outside of San Antonio to try to find answers and assistance. “The more people know, maybe it will get to the right person.”

Still, as time passes and Lucero’s sons – who were 3 and 1 at the time of her disappearance -- have grown into young men, Amanda feels helpless.

“I still feel like I felt when she first disappeared – it’s a struggle for me because she was my only sister, she was my best friend,” she said.

The family held a candlelight vigil for Lucero on November 26 to mark the 15th anniversary of her disappearance.

If you or someone you know has information about Lucero’s disappearance, call the San Antonio Police Department’s Missing Persons Unit at 210-207-7660.