I wouldn't try contacting his (maybe) people. They may worry that you will lead the cops to them. I'm sure that's why they haven't responded. Be careful please. I am sitting here trying to think of the most enticing thing to eat in this world, that maybe he will want to nibble on. I don't think Roosters care for ice cream tho. I don't know if chickens have a sense of smell but, I know my friends birds love sardines (ick!!)
Have you tried giving him baby aspirin for pain? Maybe you could dilute it and give it to him in a dropper. It might give him relief long enough to make him interested in food.
Along the same lines, mine love mashed potatoes and grits with butter and a little sugar or honey. That might be easy to eat.
Also, I just had one that finished being broody, but no baby
She wouldn't eat until I started putting the food on my fingers and holding it up for her.
they could if there is evidence of forced fighting...it is a federal offence if there is evidence the bird has been fought...but only if the authorities can get someone to claim the bird.