There will be a hidden item to shoot that will allow you out of the bonus stages. I think the stage your talking about you have to bomb the floor and it will show the opening that needs to be bombed again to clear. I know there is one stage where cats or ants or something throws strawberrys at you and that's the stage I believe the escape is in the floor.
This game is fun but the bonus stages that loop until you figure them out doesn't do anything for me. They were more of a pain than fun to figure out.