It's possible the cell phone had been disabled by water (it was found wet), or Kelly was too incapacitated to call out, or the battery went dead, or it just plain didn't work all the time for some unknown reason.
http://www.houmatoday.com/apps/pbcs.dll/article?AID=/20061216/HURBLOG/61217005
According to this article, the climber who died has been identified as Kelly James.