MESA (3TV/CBS 5) -- Kimber Biggs still has her sister Mikelle's red teddy bear, favorite picture and childhood memories
"Christmas, graduations and birthdays," Biggs said. "She's supposed to be there."
Twenty years ago this week, 11-year-old Mikelle Biggs vanished from her Mesa neighborhood while waiting for an ice cream truck.
It's a story that has attracted national attention, even now, as the case has never been solved.
"We don't have answers," said Biggs. "We don't know who took her for sure. We don't know where her body is. We don't know for sure that she is alive, or if she's passed. We have no answers and that's the hardest part about it."
Biggs, who was only 9 at the time, was the last person to see her big sister alive on Jan. 2, 1999.
The girls were outside playing. Biggs said she ran into their house briefly. When she came back out, Mikelle was gone.
"I didn't know someone had taken her, that she was missing," Biggs said. "I just knew something was wrong, and when I went home and told my mom, 'We can't find Mikelle,' her face went pale."
Over the years, the Mesa Police Department has followed up on hundreds of leads, including one back in March when a dollar bill popped up in Wisconsin.
Writing on the bill said, "My name is Mikel Biggs. I was kindnapped from Mesa Arizona. I'm alive."
But Mikelle's name was misspelled and police didn't consider it to be a credible lead.
Biggs said it's especially tough not having her sister around during the holidays, but their family refuses to give up hope that they'll find out what happened to Mikelle.
"It's like bittersweet," Biggs said. "I want to be around my family and celebrate and remember her, but it's really hard to bear sometimes. My dad has said it before, that a secret doesn't stay a secret. Someone knows something. It's just a matter of getting that someone to say something."
Mesa police Det. Steve Berry said that the case remains open and they will investigate any lead that comes in.
[SLIDESHOW: Missing children cases that rocked Arizona]