2 man crew. Bases loaded, nobody out. Batter hits fly ball to left field, which is caught. Runner on 3rd tags up and scores. Runner at 2nd leaves before the catch and also scores. Umpires said they were not paying attention to the runner on 2nd. I think I remember from other posts that Plate Ump is responsible for the catch. Field ump was watching runner on 3rd. Should the plate ump have picked up the runner on 2nd after confirming the catch, or is that not feasible?