Toland knows too much about the darkness to get lost, he's not dead because he's an all powerful warlock. Maybe he's not gone but abducted? Maybe the hive need him for information, he can speak to hive and probably knows more about the hive than the hive do themselves, but Toland has another purpose for giving them info. The hive must have something he wants desperately, and he still works as a double agent in order to obtain it. Maybe the location of Oryx?