Sithrah 3: The Symbol by Jason Brubaker

Nirvana Page won't give up hope. When a mysterious accident separates young "VONNA" from her father, she follows his trail to the wreckage of their crashed seaplane, only to find no sign of where he might've gone...or if he's even still alive. Disheartened but undeterred, Vonna and her traveling companions–DINO, a young man tortured by the secrets of his past, her irascible cat SIMON, and an invisible guardian called SITHRAH–push ever onward, encountering unexpected allies on a farm, and discovering an old piece of machinery that will forever change the course of their lives!