I've had boo splinter like that a few times.
The rind Ben is referring to is the thin waxy layer on the back there. If that's taken down too far, a splinter is possible. It's hard to tell from the picture how far it was removed. It doesn't look like it was taken down too far.
Is that moso bamboo? I used to use moso but after many splinters such as that one there, I switched to Madake bamboo and have never had a splinter since.
Yes a thin rawhide backing will work and skins are cool, but not cheap.