Richard Friedman 
Two Worlds of Billy Callahan [EPUB ebook] 

As 12-year old Billy Callahan excavates the Negev desert with his father, an earthquake sends Billy sprawling into a crevasse, where he touches a metallic orb, left here by the original inhabitants of earth millions of years ago. The orb vanishes during his rescue, concealing the evidence that could verify his incredible story.The orb sends Billy into a 50-year coma. He witnesses the first Earthlings destroy their environment and fight devastating wars before leaving Earth in shambles. The aliens release Billy, and task him to convince the modern-day world that we must avoid repeating their mistakes or life on earth will perish.