The father of a Texas girl, who disappeared from San Antonio in September 2015 when she was 6 years old, believes his ex-wife of just 34 days is hiding her.

David Hopper and Kathryn "Katie" Baldwin were married for just 34 days before they decided to split. He only learned during divorce proceedings that she was pregnant with their daughter, Ava Grace Baldwin, who is now 14 years old.

"I met her at a recovery group called Celebrate Recovery. And she had a great story — come to find out it wasn't true," Hopper, who lives in Oklahoma, told Fox News Digital. 

They had a whirlwind courtship followed by a small marriage shortly after meeting, only to file for divorce just over a month later. It was during the separation process that Baldwin said she was pregnant, but she apparently claimed Hopper was not the father. A court-ordered DNA test would prove otherwise. 

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The pair eventually began making plans to raise Ava together even though they were no longer married.

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However, after Ava was born, Baldwin moved to San Antonio and would disappear for days at a time without contacting Hopper, he recalled. The first time she went missing for days, Hopper's sister found Baldwin's MySpace profile and was able to get in touch with her through the once-popular social media platform.

A complicated custody battle began between Oklahoma and Texas, at first, and then just Texas. 

Hopper, who hired multiple lawyers in each state and spent tens of thousands of dollars in legal and travel-related costs, was granted partial custody of his daughter in May 2013 and full custody in July 2017 — two years after Ava was reported missing. That is according to Hopper's sister, Tina Hopper Fullbright, who has kept years of court records filed away in hopes of Ava's safe return.

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Ava was enrolled at a private school in San Antonio when she disappeared eight years ago.

"The principal contacted me one day and said, 'Your daughter's been missing for 21 days,'" Hopper said. That was when he officially reported his daughter missing to authorities on Sept. 17, 2015.

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Police went to the address listed as Ava's home on her school forms and found an empty lot, he explained. Hopper believes his ex-wife panicked at the thought of Hopper getting full custody of their daughter and ran off with her.

"It might be somebody — a parent — that may have a friend that [Ava] goes and sees," Hopper said of his hope that someone out there knows where Ava might be. "You just never know who that one person is. And we know that there are people who do know something."

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Baldwin's family members did not respond to inquiries from Fox News Digital.

"I think Katie thought that we were coming to court with her in October [2015]," Hopper Fullbright said. "We don't know if Katie still has Ava. We don't know if Ava's been adopted out. We don't know. We just don't know. We just believe she's alive."

Hopper Fullbright added her belief that Baldwin is using Ava as a "meal ticket."

"She uses shelters. She uses churches. [Ava]'s her meal ticket."

San Antonio police continue to investigate Ava's disappearance. SAPD told Fox News Digital that there are no new updates in the case. She was last seen on the 6000 block of Whitby Road in San Antonio, according to a missing persons flyer from SAPD.

Authorities are asking anyone with information about Ava’s disappearance to come forward and contact the SAPD Missing Persons Unit at 210-207-7660.