Please post a picture of the two of them, and an exact itinerary, with routes and the location they planned to camp at on the 11th.
There has been some monsoonal moisture effecting the Sierra all this week, which means thunderstorms and rain, were they aware of this? This could have delayed them. Any info you can provide on their clothing and equipment they were carrying (tent and pack makes and color, color of clothing)would be helpful to get the word out on the outdoor forums, hopefully someone out at the same time, saw them, and will report it to Inyo Co. Sheriff's Dept.
Have posted this on our board too: http://www.highsierratopix.com/community/viewtopic.php?f=37&t=16240