URIs are quick sometimes, and it can be hard to notice if a piggy is acting normally. I have one that I just got a few weeks ago, and she came to me with a URI from an owner that didn't want her anymore. I knew something was up, and sure enough, she had an upper respiratory infection. However, I only saw her eyes crusty once, on the day that she went to the vet's, because she is a clean piggie, and would rub them clean in a hidey house. Her old owner had no idea she was sick.
It took months for my pig Jane, that I've had for almost two years now, to trust me enough to not be afraid of my hands and run away, and truly show her personality, so in younger, hyper pigs I think it would be much harder to tell. If she had gotten a URI when younger and still afraid of me I might not have known until it was too late, because until you have spent months earning their trust, some pigs will deliberately try to hide illness, and some very sweet pigs do it instinctively anyway even if they trust you.
Its not your fault he died, it sounds like you noticed something was up even when he was still eating normally and wasn't crusty, so you actually probably noticed sooner than a lot of people would have. A good vet won't dismiss claims of " I just know something is off, even if I can't say what" so trust your instincts. Sorry about George, but it sounds like you made him happy while he was here.
