The existence of Sabal miamiensis has some doubts according to Dr. Larry Noblick (Montgomery) from a presentation he did several years ago at a South Florida Palm Society meeting. Its natural range was the coastal region of Miami-Dade County north & south of the Miami River. This corridor is now the Downtown and Brickell areas which have many high rise buildings. It is possible that some Sabal miamiensis may have survived in the few remaining old residential lots. Relying on my foggy memory, the "true" S. miamiensis closely resembles Sabal etonia. The distinguishing feature being is that they have the the most robust size fruit of any Sabal. At least according to its botanical description.
Ed - you will have to wait until it fruits. Hope springs eternally, I am one in the camp that believes the Sabal miamiensis has to be surviving somewhere. My bias does not want to accept that this palm has become extinct.