I'm very glad you are taking Mud Pie to your own vet this week because I don't like the way his toe is drawing up either. They may need to re-open the leg and have a good look inside. Cats have so many small bones in this area of the leg (according to the emergency vet who looked at a limping Ginger, my 20 year old, last week), it makes the issue very complicated. In Ginger's case, they didn't take x-rays because the combination of small bones and arthritis would have made finding the problem impossible, they said. Luckily, her's was just a sprain. I should think your vet will x-ray. Can you even be sure that this piece of bone came from the two bones that were exposed. Could it have worked its way down from another bone? It is a good sized piece and quite thick. I hope you kept it to show your vet. It must be a relief to you to see that the leg is healed and he's no longer in pain. Good luck and I will be looking for your post-vet update.