I'm sorry this happened to your sweet girl.
It makes me furious. He should have to pay every Penny of Lucy's vet bills and then some. Working in a vet clinic, I see so many of these retractable leashes and I cringe every time I see one. They are completely worthless and dangerous to the dog, its owner and the poor people and dogs that happen to be standing in the way of them. On another message board I'm on someone posted about a relative that had had her finger severed by one. They need to be banned and this idiot needs to be held accountable for his vicious dog and what happened to Lucy.