BROOKLYN, Iowa — In this Iowa town, Mollie Tibbetts' face is plastered everywhere, but the 20-year-old college student is nowhere to be seen.

"You never think you are going to see your sister on a poster with a missing sign right across it," said Jake Tibbetts, Mollie's brother.

Jake was the last to see her more than a week ago when he dropped her off at the house her boyfriend Dalton Jack lives in.

"I am just kind of putting trust and faith in the law enforcement," Jack said.

This undated photo released by the Iowa Department of Criminal Investigation shows Mollie Tibbetts. Iowa Department of Criminal Investigation via AP

He was out of town at the time of the disappearance and is not a suspect. Tibbetts went out on her usual evening run but never showed up at work the next day. Search teams have fanned out in the area and on her usual running routes. Now 15 FBI agents have also joined the investigation and officials are looking into Tibbetts' Fitbit and social media footprint for clues to build a timeline.

"That takes it to a whole new level, because we're hoping to be able to precisely examine and know where she was, when she was there," said Mitch Mortvedt, special agent in charge with the Iowa Division of Criminal Investigation.

Tibbetts' Fitbit could potentially give investigators a trove of data on the day she disappeared using GPS technology and other data like her heart rate. Investigators have also issued warrants to social media companies for data that could help determine exactly where she went.

"You can actually overlay the location data with the real world to find out what exactly happened," Thomas Yohannan, an expert on data recovery. "You are essentially trying to find a witness to the events that happened leading up to her missing person."

Late Thursday, investigators said they had completed reconstructing their timeline of Mollie's run, relying on Fitbit data, cell phone pings and eyewitnesses.