Where in the world is Robert Pattinson? The unexpected answer, as revealed in the new Us Weekly, is Reese Witherspoon's vacation house.

The Twilight star, 26, has gone AWOL ever since he discovered that his longtime love Kristen Stewart cheated on him with director Rupert Sanders on July 17 (with Us Weekly first revealing the shocking pics July 24). False online reports claimed a U-Haul truck was spotted outside the L.A.-area home he shared with Stewart, 22, and that Pattinson had retreated to his native London to party with pals.

The real story? When the devastated Brit needed to get away from it all, his Water for Elephants costar Witherspoon, 36, offered up her tranquil, $7 million ranch in Ojai, Calif.  (The pregnant actress wed husband Jim Toth in March 2011 at the rustic chic estate, recently featured in ELLE Decor.)

As Pattinson attempts to relax chez Witherspoon, he is, according to another source, "a total mess . . . He's questioning everything."

An "inconsolable" Stewart, meanwhile, has been reaching out via texts and phone calls.  "She's dying to save the relationship. It's the only thing she cares about," a Stewart source says.

Indeed, Pattinson, who fell for his Twilight costar nearly five years ago, "doesn't know what to do." says a concerned friend.

For more exclusive details on the Stewart-Pattinson scandal -- how he found out, Stewart's suspicious behavior before her fling was discovered, Stewart and Sanders' chemistry on the Snow White and the Huntsman set, and more -- pick up the new Us Weekly, on stands Friday!