Laura Calderwood said she refuses to give up hope.
The mother of Mollie Tibbetts spoke out in an exclusive interview with ABC News after her 20-year-old daughter had been missing for nine days.
Calderwood discovered Tibbetts was missing when she received a phone call from her son, Scott, who said, "Mom, did you know Mollie didn't go to work?"
Tibbetts, a University of Iowa freshman, didn't turn up at work in Brooklyn Iowa, where she's living over the summer with her boyfriend, Dalton Jack.
"That is so out of Mollie's character, one, not to show up for work, two, not to let her employer know, and, three, boyfriend, myself and her brother -- just no one was notified that she didn't go to work," Calderwood said. "There were alarms going off immediately. ... Within 15 to 20 minutes of me coming home ... there were a bunch of her friends and I could see they were worried ... within 15 to 20 minutes, I called 911."
A witness spotted Tibbetts running on the afternoon of her disappearance, police said, which adds to the mystery.
"It's just been excruciating ... mind numbing ... all of the range of emotions," Calderwood said.
Calderwood thanked members of community for their support during this difficult time.
"The community has gone above and beyond," she added. "We have had, you know, all kinds of food and water and Gatorade from family and friends, and I know that the investigators down at the police station are overwhelmed with what the community has done."
Volunteers combed through corn fields near Tibbetts' jogging route but so no sign of the 20-year-old. Authorities are now analyzing her digital footprint, including Fitbit data.
Throughout it all, Calderwood remains hopeful.
"If it were me that were missing, Mollie wouldn't give up hope -- that's not even a thought," she said. "You won't see me giving up hope. That's not an option."