According to the Academy, George C. Scott’s Academy Award for ‘Patton’ (1970) is still in their vaults, presumably so that he could claim it at some latter date. Of course, now that he’s gone, there’s little chance of that happening.
I do recall the Academy President at the time brushing off the snub by saying that the Oscar was awarded for a performance and that recognition stands, whether or not a performer choses to acknowledge it.
Also, you’re confusing two different Oscar refusals. George C. Scott’s Oscar was quietly accepted by Patton’s producer Frank McCarthy (and later returned to the Academy). Marlon Brando refused to accept his Award for ‘The Godfather’ (1972) and sent “Sacheen Littlefeather” in his place to make a protest against American Indian portrayals on film. Littlefeather, as it turns out, was not an indian at all, but Maria Cruz, a minor actress hired to play the part.
And finally, all of the Oscars handed out on Oscar night are identical. Nothing is inscribed on the base until after the ceremony. In fact, the winners have to return their statuettes at some point so they can be personalized.