For a wedding that was organized in a few days, high-school sweethearts Jaime Mullin and Anthony Parchesky seemed ready to say “I do.’’

Mullin, 20, had a white dress with a peach, floral print from Kohl’s and a beautiful bouquet that her aunt and uncle assembled. Parchesky, a US Army specialist home in Medway on leave, wore a white dress shirt, navy blue pants and a matching tie, and a boutonniere.

But when the justice of the peace showed up at Mullin’s house in Milford on Thursday evening and asked for their marriage license, the couple realized they had a problem. That very important piece of paper was locked in an office at Medway Town Hall.

“We just both forgot,’’ Mullin, a Framingham State University student, said Friday. “I don’t know how, but we just forgot.’’

It was after 5 p.m. The guests were arriving. And Town Hall was closed.

Time was of the essence because Parchesky, 20, who recently returned from a nine-month deployment to Afghanistan, is scheduled to return Sunday to his post in Fort Hood, Texas.

To start their married life in the military, the couple needed to present officials at Fort Devens with a stamped marriage license by Friday.

“I was in a panic,’’ Mullin said, who took her husband’s last name.

Parchesky called his mother, Denise Oakes, who was driving to the wedding.

“I forgot to pick up the license,’’ he told her.

“Oh my God,’’ she told him. “The registry is closed.’’

Oakes, 38, pulled over and called town hall. No one answered. She posted a plea to Friends of Medway, a Facebook page in which members seek recommendations about home contractors, post information about local traffic, or share details about community events.

“I need a huge favor,’’ Oakes wrote at 5:03 p.m. “My son is getting married tonight and he forgot to pick up the marriage license. Can someone open the Town Hall for me????? PLEASE!!!’’

Seven minutes later, Robin Burroughs, who didn’t know Oakes, chimed in. She saw the Facebook post and called a friend, Joanne Russo, Medway’s treasurer-collector.

Luckily, Russo was still at work. She found Donna Greenwood, the principal assessor, working down the hall and she had a spare key to the town clerk’s office, Russo said.

Greenwood called the town clerk on her cellphone and got permission to open the office. The license was sitting on a desk, she said. Russo called Burroughs with the update.

“All set Denise,’’ Burroughs posted to Facebook at 5:17 p.m., telling Oakes to seek out Russo at town hall. “[S]he has it for you! Congratulations to your son!’’

Oakes said she got the news from her husband, Gary, who was monitoring Facebook as they drove to town hall. Parchesky and Mullin also saw Burroughs’s update as they waited in the living room where they planned to wed.

“I said, ‘We have it, everyone! We’re good,’ ’’ Mullin said. She “looked like a 1,000-pound weight was lifted off her shoulders,’’ Parchesky said.

At town hall, Oakes ran into Greenwood at the back door and retrieved the license inside.

“I took the biggest deep breath,’’ said Oakes, a lifelong Medway resident. “I was just like, ‘OK. Let’s go.’ ’’

A short time later, Oakes arrived at Mullin’s home, where the bride went outside to meet her, and the marriage license.

“I gave her a big hug,’’ Mullin said. “I was like, ‘You saved me!’ ’’

The wedding ceremony started at 6 p.m. After vows were exchanged, guests dined on food prepared by Mullin’s mother and a local caterer, including chicken Parmesan, ham, and salad.

At 6:23 p.m., Oakes posted a photograph on Facebook of the newlyweds’ first kiss.

The Friends of Medway rejoiced.

“I’m grateful that we live in such an amazing town,’’ Oakes said. “You wouldn’t be able to get that treatment if you lived in a big city unless you really knew somebody.’’

The wedding capped Parchesky’s three-week military leave, during which the couple got engaged over dinner at Top of the Hub in Boston on March 9. On Sunday, they said they decided to marry before Parchesky returned to Fort Hood.

The couple said they plan to host a more traditional wedding in the summer of 2018.

But for now Mullin and Parchesky, who graduated from Medway High School in 2014, said they’re thankful for the hometown help.

“It’s really awesome,’’ Parchesky said. “The people of Medway are great people.’’

Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi.