Story highlights Olivia Campbell, 15, had been talking about the Ariana Grande concert for weeks

More than 150,000 people shared posts seeking information about Olivia

(CNN) The mother's dread and fear gripped parents around the world in less than a day.

For 24 hours, Charlotte Campbell suffered the most harrowing anxiety imaginable. Her daughter, 15-year-old Olivia Campbell, didn't pick up her phone after the gruesome attack outside an Ariana Grande concert

Sobbing, Charlotte Campbell took to international airwaves, pleading for anyone who may have seen Olivia to please come forward.

JUST WATCHED Mom: I don't know if she's dead or alive Replay More Videos ... MUST WATCH Mom: I don't know if she's dead or alive 01:22

"It's the most horrible feeling ever -- to know that your daughter's there, you can't find her, you don't know whether she's dead or alive," she told CNN's Don Lemon shortly after the Monday night blast.

Within hours, more than 150,000 people shared Campbell's Facebook posts asking for information.