Umbrella singer Rihanna was going it alone last night at the California Speedway event at Club Avalon.  She showed up without her new beau, Indiana Jones 4 star Shia LaBeouf, but she did have a posse of pals in tow. The R&B phenom – who’s still recovering from a broken foot – was forced to drive to a cop station for help when a crowd of fans mobbed her and followed her car after the event, we’re told.