We had a cat once that "adopted" us, cat owners will know what I'm talking about. He actually belonged to a dude up the street, he would walk by and see his cat in our window. We kind of knew him, he did mention once that he paid "a lot of money" for that cat. The cat wasn't any fancy breed, just a common or garden moggie. We told him that his cat was friends with our cat, and he didn't really mind I guess, his cat used to climb out of a high window to get out, what does that tell you?
Not long after, my parents went away, and I had the place to myself. No wild parties, I was in my early teens, so my friend came over and bought his computer with him, we played computer games all night and drank the beer we somehow managed to procure. Anyway, so the cat came in, my friend picked him up and got covered in blood. We had a look at him, and there was a very deep cut right by his tail, you could almost see right inside. It was very late, I didn't know what to do, so I made him comfortable and went to bed. I got up early next morning, and with a hangover took the cat on the bus to the vets. The vet said it looked like he had been bitten by a fox, he was probably being chased and the fox managed to get in a bite, hence it was on his behind. They stitched him up and I brought him home.
Sorry to hear about your cat.
Lee.