I attended countless occasions (more than 30) of Mosconi's exhibition performances, and some of his rare post-war competitive performances.The story I've heard is a fire at Willies house destroyed all the film of him.
I always thought that maybe some where in a Brunswick building or a former Brunswick employee has some old forgotten films.
It's also possible that Brunswick tossed it out at one point in time.
Willie generally insisted to venue hosts that no unauthorized hand-held filming be allowed for spectators. He had several career-protective reasons for the caveat, including potential distraction, profiteering, and the potential for capturing what his obsessive (and beneficial) perfectionism would term: unforgivable misjudgments or faulty execution on his part. Meaning less than automaton, flawed-human playing, in his view. A view that gave us a legacy of near-magical runs that made it all look so easy, and exhibiting the logic and sustained excellence so uniquely characteristic of historic Straight Pool.
Arnaldo ~ One day there will definitely be the technology to harmlessly extract and digitalize the memory bank of my kindred geezers -- I foolishly presume to speak for -- who have these precious memories of a nonpareil performance genius mesmerizing spectators.