Has anyone ever found the missing Ambersons footage?
No. The cut footage was kept in film vaults for a few months, and was eventually burned due to a shortage of storage space. There are lots of stills from the cut footage, and the movie trailer (which is on the VHS tape from Turner Classic Movies) has a few seconds of film that isn’t in the movie. The January 2002 issue of Vanity Fair magazine has a great article on Ambersons, including interviews with several people who have tried unsuccessfully to find the original version, both in the US and South America. Although no one can say for sure that the missing footage no longer exists, the take-home message of the article is that it’s gone for good.