Hi OP,
some years ago we had a similar thing happen to one of our cats. We'd been out or the day and when we got home, Brian was laid under a chair by the back door and couldn't get up. Could move to a sort of sitting position but his back legs and tail were totally none moving and unresponsive to touch. Got him to the vets where he stayed for 4 days. They think he'd been hit by a car (although they weren't sure as he didn't have the scruffs on his claws like they usually do). He'd broken his pelvis straight through the middle, snapped the head of one if his femurs off and smashed it, broken the other leg and a couple of bones in his tail.
When we got him home, he had to be kept in a crate for 6 weeks. We borrowed a large dog crate from our neighbours. He had a litter area in there. After about 4 weeks he could walk but not very well, after 6 he was jumping up on furniture and stealing food from the work tops. He always had one leg shorted than the other, but apart from that he was fine and could get around no problem. The nerve damage did take a while to heal properly- he was alright at the front, but his back end looked like a drunk for around 4 months.
Not sure how veterinary stuff has moved on since as it's about 14 years since it happened. He didn't have an operation as the pelvis they reckoned would heal in it's own time and the head of the femur was so badly smashed that it wasn't possible to put it together again. His other leg could have been plated if that was the only injury, but because of the pelvis break it would have put too much pressure on it. The femur formed a "false" joint which is what made his leg a bit shorted than the other.
So there you go. He made a fullish recovery from a bad accident and got back to his normal self within 6 weeks. Amazing the power of recovery they have. Hoping your little kitty is on the mend soon.