Who the *$&% Is Jackson Pollock? (2006)
Who the #$&% Is Jackson Pollock? is a documentary following a woman named Teri Horton, a 73-year-old former long-haul truck driver from California, who purchased a painting from a thrift shop for $5, only later to find out that it may be a Jackson Pollock painting; she had no clue at the time who Jackson Pollock was, hence the name of the film.
More at Wikipedia.