You need to see how the source metadata was tracked on the orignal offline clips. In your bin, create a bin view that includes the following columns:
1. Tape
2. Source File
3. Start
4. End
Depending on the process, there will be a filename in the either the Tape or Source File column. If Tape, then it was done as part of a dailies process with third party software. If in Source Files, then they probably linked via AMA and transcoded. Once you know what that is, we can advise how to do a relink. It is not the most obvious process, but you can usually get it to work after multiple attempts… 🙂
Michael