Tyler Tessier, left, the boyfriend of missing Laura Elizabeth Wallen, at a news conference with her parents, Gwen Wallen and Mark Wallen. (Michael Robinson Chavez/The Washington Post)

The father of a missing pregnant teacher passionately pleaded Monday for help finding his 31-year-old daughter, his appeal conveying the torment of not knowing what has happened to her.

Mark Wallen begged anyone who might know where his daughter is located to speak up — and then, on the chance Laura Elizabeth Wallen could hear him, begged her to call.

"We miss her, we love her, and it's one of the hardest things a father can do is to have a child taken away, way, way too soon," Mark Wallen said at a news conference at Montgomery County police headquarters. "All we want is her to come back to us. Laura, if you're out there listening, pick up the phone. Whoever might be helping and hiding her, please come forward and make it happen."

It's been a week since the family heard from Laura Wallen, who is four months pregnant and a teacher in Howard County at Wilde Lake High School, where she failed to show up for the first day of classes Tuesday after several weeks of preparing her classroom.

On Thursday, police found Wallen's car, unoccupied and parked in an apartment complex in the 10600 block of Gramercy Place in Columbia, a five-minute drive from the school.

Mark Wallen said the family is offering a $25,000 reward for anyone who provides information that leads to the safe return of his daughter. Sitting behind him was Laura Wallen's mother, sister, brother-in-law and her boyfriend, who is the father of the baby she is carrying.

Laura Elizabeth Wallen, 31. (Montgomery County Police Department/Montgomery County Police Department)

"She is still alive somewhere," Mark Wallen said.

Lt. Sean Gagen, deputy director of the major crimes division, said county police are still investigating her disappearance as a missing-person report and do not have a reason at this point to believe there has been foul play.

But "as each day passes, we become increasingly concerned for Laura Wallen and her baby," Gagen said.

The last contact from the teacher was a text message Sept. 4 to her family that concerned them enough that they called police, police have said.

Police have declined to say what the text said and on Monday also declined to say to whom it was sent, whether investigators knew of any connection between Laura Wallen, of Olney, and anyone at the apartment complex where her black 2011 Ford Escape was found and when and where she was last seen.

Mark Wallen said he became certain something was awry when he called Wilde Lake High School on Tuesday morning to check if his daughter had arrived and was told she had not. He then asked if she had arranged for a substitute teacher and was told no — a lapse he said he was sure she would not have made had she known she would be absent.

Her boyfriend, Tyler Tessier, said she was "super excited" for the start of the school year and called her disappearance a "complete shock." He said the two had gone to doctor appointments together and that she was happy about the pregnancy.

"Laura, if you're listening, it doesn't matter what's happened. It doesn't matter what type of trouble. There's nothing we can't fix together," Tessier said, ". . . we haven't slept, we haven't eaten, we're just looking, we're praying that you're safe. I'm asking you to just let us know that you're safe. If somebody has her, please understand that you've taken away a huge person in so many people's lives."

Tessier said he and his girlfriend have known each other for about 10 years.

Asked by a reporter if he recalled the last conversation he had with her, Tessier said, "I don't know where she is, that's all. I don't know. . . . I'll try to do everything we can to find her. I just pray that . . . I pray that she's safe and she comes back. That's all I care about right now."

Wilde Lake Principal Rick Wilson called Wallen "an amazing young lady."

"At this time, the Wilde Lake community is focused on assisting with efforts to locate her and praying for her safe return," Wilson wrote Saturday in an interview by email.

Last year, Wallen was recognized as the Wilde Lake High School senior class's teacher of the year, according to the school's Twitter account.

When Mary Weber's now 16-year-old son was in seventh grade, he told Wallen he liked to skateboard. So Wallen, who was his social studies teacher, told him she would rummage through her belongings to find her skateboard and ride down their street.

Sure enough, Wallen showed up at their house with a skateboard. It was hilarious, Weber said, but it was "just typical Laura."

"It put such a smile on our face. It just made my son's day," Weber, 50, said Friday.

The teacher also had an impact on Alicia Waxman's son when she taught him social studies in seventh grade. She thought he was funny, so encouraged him to play the genie in the school's production of "Aladdin," and last spring, knowing his love of history, urged him to join a school trip to Europe focusing on World War II.

"She had a way of putting a bright light on everybody else," Waxman, 43, said Friday. "She focused on what was good about you and she magnified it."

Waxman said she had lunch with Laura Wallen three weeks ago and the teacher told her she was pregnant. The two have been friends for five years and Waxman said the teacher was "really excited to be a mom."