Is my cats leg paralyzed?

My cat got hit by a car three weeks ago. I took him to the vet right after he got hit and the vet said over the phone he had a dislocated hip. Then, when I went to pick him up, the vet said he had taken x-rays and that my cat had a broken pelvis. He told me that it would be about six weeks before he was completely healed and gave me a bottle of Arnica. My cat seems to be alot better now, except that he doesn't use his left leg at all. It is completely limp and he drags it along when he walks. The muscles on the upper part of the leg are all sunken in. Did the vet miss something??