How do I get iTunes to recognize that the previous location of my movie files is permanently gone?

The external hard drive I had connected to my Airport Extreme, which I used as a download location for my iTunes movies, died recently. Now my iTunes library doesn't show artwork for movies and tries to locate a file which no longer exists when I try to play movies. How do I get iTunes to recognize that there is no physical file anymore and let me stream the film without attempting to locate it first?

I have removed downloads for movies, no luck. I have changed the media folder location in hopes of creating a blank slate, no luck. I know I could just download the films to a new HDD and solve the problem, but I have no interest in downloading a few terabytes of films again. I'd rather just stream from my computer like they were never downloaded. What can I do to essentially reset my library?