If you used UTF-8 then you can probably fix those pretty easily. UTF-8 is sufficiently structured that it’s extremely unlikely for a string that’s written in another encoding to be valid UTF-8 by accident. If you write some code to try decoding as UTF-8 and set that as the encoding when it succeeds, you’re unlikely to damage anything in the process.
I've run into similar problems when moving old content between systems, especially with MySQL and mixed encodings. It can get messy surprisingly quickly.