You are spot on and it's exactly my take on it all too.
Please may I add that I have hunted fox's for 4 decades with several centerfires from .224" through to .357" and believe me, even with them you will get a cock up of a shot and a fox that does not drop to the shot, I promise.
Personally when it has happened I return asap to try and retrace the event.
As crazy as it sounds the worst time I had was with a friend 22-250!! We had several fails. It was not good. Does that mean I think 22-250 is rubbish? No, certainly not.
It was just a combination of bullet choice, powder choice and rifle choice. As soon as we changed bullets and powder success returned to normal.
I'm simply relating this to demonstrate there is always somewhere,somehow, an exception to the rule!