No, no.....Gappy may have a valid point. There's many an occasion something lying on it's back with it's feet in the air has been mistaken for having rolled a six...
Get the water tested and if OK buy another one. Would Mum notice the difference ? ( bet I know the answer to the question)
Bladder gill infection....that fish was alive, until you buried it. the lesser orange guppy goldfish does this when it has an infection, it would have been right as rain with a warm water change from the tap into the tank. however, you've murdered it.
On the Scale of things I think You'v Haddic with this Place its too Hakeful. People are Carping on Porpoise about your floundering to help poor Oscar.