I really don't know how to call this one. 5 PA retrieves a body, but that doesn't cover extra planar travel. That is really a tricky one, and I'd like to see the official answer to this. Though why the escapee decided to leave his friend behind is also puzzling.
I think it may have been a mid combat Vanish (as it was a ninja) run away and hide type thing
it wasnt my table so I really dont know the specifics ...
Plane Shift is a 5th lvl Spell and I would assume that the fork's cost stayed the same (I just woke up and search fu is weak) at 500 so theoretically one could calculate the cost of the spell + Fork
lvl 9*5(5th lvl spell)*10 = 450*2(cost to get home) + 500 (planar fork shadow plane) MAYBE another 500 for the fork to get home as well
1900gp for just the travel portion ... assuming my cost is right
I would rule that they had died during the branding process. Oops, I slipped and stabbed you in the eye, you were at -9, sorry. Then if they can afford the body retrieval and raise, or a true resurrect, awesome. If not, sorry, your character is done, and if you prefer to think of him/her as forever enslaved on the shadow plane rather than actually dead, that's your call.
While the body retrieval probably isn't intended for planar travel situations, we are Pathfinders, after all ... and the Shadow Plane isn't that far from Absalom, when you get right down to it.
And while the ruling might be harsh, we are Pathfinders, after all. These things do happen.
When the two planes conjoin while the Wightir Conjunction remains active, elements of both planes may be treated
as real and interact with one another, but upon the device’s deactivation, all creatures return to their plane of origin.
So the choices the Shadow plane creatures were faced with were to kill the prisoner, Spend healing on the prisoner and then brand him, or let him shift back into his home plane. Make a call or roll randomly to determine his fate.