It could have been "A Blind Bargain", which is allegedly more of a horror film than "London After Midnight". Also many film historians think "The Miracle Man" is probably the best/most important lost Chaney film but that's a drama, not horror. "London After Midnight" doesn't really sound that great from the info we have on it. Allegedly a lot of the film is more comedic, with Chaney as the Inspector (not in the "Man in the Beaver Hat" disguise).