I'd seek a second opinion on the records from a vet who advertises as cat friendly. Our vet does and I very much trust her judgement.
It may get you you the same advice, some internal injury that was just beyond the first vet's ability to help.
Very sorry to read of the loss of Binx.
I would consider speaking to someone at the vet's licensing board to ask how normal this all is.
Thank you for your response. I was there to see the x-rays and the vet said she didn't see any ribs broken to cause a puncher. She said it could be a very small or large hole. Nothing about organ damage.It was just heart wrenching to hear my girlfriend say how Binx wanted her to help him and he wanted to live but everyone told her she was doing the right thing by ending his pain so she sad yea .I mean here this cat that doesn't mean a thing to anyone except this lady thats heart broken crying uncontrollably, the vet made its $500 already so their done (they don't do that kind of surgery.) I mean what heck put him down and say oh he's in a better place and not in pain any more. We very much trust the vet. Sorry i guess i just dont feel we did enough, i should of been there and not been so ignorant about the whole thing. But you know what really got me was when we first walked in with this poor little guy that just got hit buy a 2000 pound rock going 45 mph and they want the paper work done and this dog to get his shots first. Thanks i hope this made sense.
From what I can find online, there are various degrees of severity of pneumothorax. Some sound like they are treated by the chest tube, but others sound like they involve the heart and other organs and are more or less hopeless. Did the vet talk to you about any of this, and why he or she euthanized? (Do you know for sure the vet didn't talk to your spouse and in fact get approval to euthanize?) You could certainly ask for the cat's records to be sent to another vet, if you are mistrustful of the situation.