Stranded - The Daniel Archer Journals, #2

Using the SPIRIT device he'd stolen from Marchant Electronics, Daniel sets out to rescue his friend Tomas from his kidnapper the villain Sam Creech. Creech's intention was to use his hostage to get his hands on the same device by offering the teenager in exchange. Although Daniel's plan was a simple one, it should have been straightforward, returning the two boys to the armoury at Dreary palace. However, when Daniel arrives back at the palace, there's no sign of Tomas.
After several moments of agonized thought, he concludes that as he'd only been there ethereally using his astral projection ability, he'd had no physical contact with his friend, so the SPIRIT hadn't been able to transport Tomas leaving him still with Creech. With only one course of action open to him, he decides to return to where Tomas was being held only this time travelling there physically all the while hoping Creech hasn't removed Tomas to another place following his first failed rescue attempt. Rather than giving the kidnapper time to move Tomas or carry out his threat to kill him, Daniel checks the SPIRIT to ensure its setting remain correct which is when he discovers what had happened.
All were as they should be except the year setting, which he'd somehow forgotten to lock allowing it to become changed when he stuffed the device into his jeans pocket.  Instead of returning his friend to the palace, he's sent Tomas back seven hundred years into the past. Knowing that Tomas has no way of time travelling without a SPIRIT, Daniel does the only thing he can and travels back himself to collect his friend.
Arriving in time to find Tomas about to go searching for him he tells him what has happened and explains that they are still in Verania but in the year 1503. Before they have time to activate the device to return to 2203, an armour-clad knight confronts them, angry at finding them in his chambers.