Scarlett Johansson was chatting up Sean Penn at the party Javier Bardem hosted last weekend for “Black Swan” at Hollywood’s Sunset Tower Hotel. But a rep for Johansson, who’s divorcing Ryan Reynolds, said a rumor she and Penn left together was “not true. She went home after the party and they did not leave at the same time.” A source said Penn left on his own and went on to Dan Tana’s to meet some guy friends.