INDIANAPOLIS -- The pain of losing a loved one can cause unimaginable grief – but not knowing can be even worse.

For millions of families, including the parents of IU student Lauren Spierer, that pain and fear is present every day as they search for their missing loved ones.

GALLERY | Can you help solve an Indiana Missing Persons case?

This June will mark five years since then-20-year-old Spierer disappeared after a night out partying with friends in Bloomington.

Police have followed countless leads to no avail, and Spierer remains missing to this day.

Across the country, police get assistance in missing persons searches from people like David Rader, who works for Texas Equusearch – a non-profit search and recovery team. Rader has helped lead hundreds of searches – starting with the disappearance of Florida toddler Caylee Anthony.

"So, basically what you want to do is start from where the person was last physically seen, and then you work your circle from there until different intelligence comes about to put you in a different area," Rader said.

Rader uses technology to his advantage during those searches: drones in the sky; ATVs on the ground; and radar in the water.

Family members like Sarah Copley say they'll use any resource available. She's eight months in to her search for her sister Whitney, who disappeared after a party in Southern Kentucky in September.

"She never read my message, never opened it, never replied and I knew something was wrong," Copley said.

Whitney isn't just Copley's sister – she's also a mom to 2-year-old Serenity and 7-year-old Adelyn.

"I don't want her daughter to look at her aunt and say, 'What happened to my mom?' and us not be able to tell her," Copley said. "Because at this point, we don't know. We can't tell her she's is dead, she's alive, she's coming home, she's not … because we don't know what to say."

Websites like NamUs, the National Missing and Unidentified Persons System are another outlet families search. Thousands of families have found answers on the site – but as of 2014, as many as 90,000 active missing persons cases still stood

Experts say if you find yourself in Copley's position and cannot find a loved one, you should follow these tips:

First and foremost, call the police

Gather recent photos and videos available

If the missing person is a child, have any relevant parental paperwork handy, including background information and paperwork for domestic situations.

Also, provide authorities with DNA of that person, if you have any.