Accidentally deleted my song ratings - how can I get them back?

First off, I hate, HATE the stupid album rating system that was artificially inserting songs into my ratings (5 stars, 4+ stars, etc.) smart lists. So I tried to follow a suggestion and rate all my albums as zero / none stars to get them off my playlists.

However, it appears to have changed the ratings for my entire library to zero stars and now I'm missing 12 years worth of ratings. 😠

Please, for the love of God, tell me I don't have to go back and try to manually rate several thousand songs again from memory.