Update: I fixed it! Here's what I did, incorporating _durin_'s advice.
1. Copied the track that needed changing into a new multitrack session.
2. Went into the XML file of that session, changing it to the file I needed.
3. Copied the fixed track back into my original multitrack.
4. Danced around my apartment with joy.
So I hope that helps anybody with my trouble in the future.