Renaming an event in iMovie and yellow warning triangles

Im new to the world of apple and iMovie and have made the mistake of completing a project and then renaming my events to tidy things up. I've since been told that this was a stupid thing to do and my project cannot locate the footage from the event (even though the footage still exists in the newly renamed event folder).

How can I relinking the footage back so that the project recognises it again? Or will I have to create it all over again? The project was two hours long so I really want to try a d avoid redoing it.