The parents of a Kansas teenager whose shocking murder nearly a decade ago inspired legislative calls for cellphone carriers to give police phone records in life-or-death situations told FoxNews.com they remain resolved to getting the Kelsey Smith Act passed in Congress -- after the House voted it down Monday. 

Smith was 18 when she was abducted in broad daylight outside a Kansas shopping mall in 2007 and strangled. The teen's parents spent four harrowing days looking for their daughter, but the search would have ended much sooner had Verizon Wireless promptly handed over cellphone records to authorities.

Current federal law allows cellphone companies to release information to police in certain situations, but it does not require them to do so. The Kelsey Smith Act mandates it -- and has become law in 22 states since the young woman's death.

But a national version of the bill failed Monday in the U.S. House on a 229-158 vote amid privacy concerns; it required 290 to pass. 

"We're not giving up," Kelsey's mother Missey Smith said Wednesday. "Kelsey is the force behind this and it will happen. It may not be this year, but it will happen."  

Opponents of the measure, like the American Civil Liberties Union, argue the law takes away a phone company's discretion in providing cell phone information to law enforcement. It also prevents cell phone customers from suing companies for releasing the information without good reason, according to critics.

ACLU Legislative Counsel Neema Singh Guliani said in a statement that the House vote demonstrates that lawmakers realize the current version of the bill "opens the door to law enforcement abuse," adding: "It would require companies to turn over information – even in cases where they have evidence that no real emergency exists." 

But Smith countered that the law in many places leaves it up to a customer service representative to determine what constitutes an emergency. 

"They're not trained law enforcement. And we don't even know if they're in this country," she said. 

Responding to critics who cite the Fourth Amendment in opposing the bill, she said: "The Fourth Amendment is about unreasonable search and seizure. There is nothing unreasonable when someone is missing."  

Kansas was the first state to implement the law in April 2009, followed by New Jersey, Nebraska, Minnesota and New Hampshire in 2010. 

The law proved critical on a February evening in 2015 when a Kansas mother's car was stolen with her five-month-old baby and cell phone inside. Because of Kelsey's Law, officers were able to obtain the woman's phone information immediately, and the baby was found, unharmed, in less than 40 minutes.

Smith, who just 10 days prior had graduated from high school, was forced into her car by 26-year-old Edwin Roy "Jack" Hall as she walked through the parking lot of a Target store behind the Oak Park Mall in Overland Park, Kansas, on June 2, 2007. Hall drove Smith 20 miles across state lines to Missouri, where he raped and strangled the young woman with her own belt, leaving her body covered in brush in the woods near a lake.

Smith's parents acknowledge their daughter was likely dead by the time authorities were notified of her disappearance – and that any information obtained by Verizon would not have changed that outcome. 

“It would not have saved Kelsey’s life,” Missey Smith said of the federal law she is advocating. “But it would have saved us four days of agony not knowing where our child was.”

Verizon eventually released the information four days after she disappeared, and her body was found within an hour.

The federal bill, H.R. 4889, allows for police to obtain phone information without a search warrant in situations involving “risk of death or serious physical injury.”

The driving force for the legislation in Congress is Republican Rep. Kevin Yoder, the bill's sponsor who represents Overland Park, where Smith was from. Three other House members -- Republican U.S. Reps. Lynn Jenkins and Mike Pompeo, of Kansas, and U.S. Rep. Emanuel Cleaver, a Democrat from Missouri -- are co-sponsors.

Yoder said Wednesday the benefits of the legislation far outweigh privacy concerns.

"I think, understandably, members of Congress are cautious about giving law enforcement tools that could be abused," Yoder told FoxNews.com. "But in this case, that’s really not a possibility. We’re talking about narrow circumstances -- life or death situations."

Yoder said he remains confident the bill will eventually be passed into law nationally.

"The support for this legislation is growing," he said.

"Most of us in Congress are parents," Yoder said. "When you put yourself in the shoes of the Smith family, how could you not have compassion? How could you not want this tool available if your child were missing?" 

Cristina Corbin is a New York-based reporter for FoxNews.com. Follow her on Twitter @Cristina Corbin.