Not sure if there is a thread yet on here. But her case has always intrigued me.
Elizabeth Campbell was the college student who disappeared from a pay phone, later on she is seen under the control of a mysterious man.

I would love to hear all of your theories regarding this case.

here's a thread:

http://www.sitcomsonline.com/boards/showthread.php?t=138696&highlight=elizabeth+campbell

fun fact: This was thread #7,777 on the UM forum.