ST. LOUIS (AP) — The horror of the killing grabbed headlines: After her car breaks down along an Illinois freeway, a college student described by her mom as an all-American "girly girl" is snatched up, sexually attacked and repeatedly stabbed, perhaps by a trucker posing as a good Samaritan.

Tammy Zywicki's body eventually turned up in a blanket wrapped with duct tape in southwestern Missouri, hundreds of miles from where she was last seen alive.

Now two decades later, the killer remains elusive, and federal and Illinois investigators hope a $50,000 reward changes that. On Wednesday, the eve of the 20th anniversary of Zywicki's disappearance, the head of Illinois State Police insisted investigators haven't forgotten the vexing case.