Henry Hobbs and the Lost Planet by Kathryn Cave
There's an emergency on Henry Hobbs' home planet, Omicron - and Henry's in the thick of it. But it can't be his fault, because he's done nothing wrong. So why is he getting messages for the Lord of Michor, and what exactly is this 'tercon' they keep mentioning? Before Henry can discover the answers, he disappears. Only to find himself all alone on a lost planet - or is he?