So the cat is doing better...
But only because it turns out the vet had not done a full x-ray like they'd told us. It looked like the only thing it could be was brain damage because they "couldn't find a scratch on him" and he was stumbling around like a little drunkard. Now he's gotten over the worst of the concussion, you can see he's not just disorientated, he's holding his leg at a funny angle.
Fortunately, we'd already moved vets before we even found out about the lack of full x-ray. And new vet was like, hmm looks like a broken pelvis... Why didn't the x-rays pick up on that? Well that's because imaginary x-rays don't give very clear images.
So there will be another round of x-rays tomorrow and hopefully some kind of refund for my parents from the first vet who lied and wasted our time.