In theory, Unknown White Male ought to be a fascinating movie. It’s a documentary about Doug Bruce, who on the morning of July 3, 2003, found himself on a subway to Coney Island, unable to remember…anything. Diagnosed with retrograde amnesia, he becomes, in effect, a true-life counterpart to the Guy Pearce character in Memento. Except that Unknown White Male isn’t a thriller (in any sense). Bruce, in a matter of weeks, learns the basic facts of who he was — or still is: a 33-year-old British expatriate who made a fortune as a stockbroker and lives in an East Village loft. He meets his old buddies and girlfriends and watches home videos of himself — but none of this rings the faintest bell of recognition in the newly blank space that is his mind. Unknown White Male is framed as a look at the mystery of identity, but there’s a bizarre neutrality to the movie, since it makes Bruce’s life just as detached and remote to us as it seems to him. Everything under the sun — chocolate mousse, the Rolling Stones — is new to his senses, yet the filmmaker, Rupert Murray, who knew Bruce before the amnesia struck, probes his pal’s predicament without ever piercing the membrane of his unnerving experience.