If you have CDC and no replication, then there's technically no 'unreplicated' transaction as it's CDC that's behind/failing, not replication. They use the same method to get transactions, that's why this looks like replication.

As for identifying what the operation was, you could read the transaction log if you're feeling very brave. That's pretty much it unless you had something tracing commands run that you can go back through and look at (opentran gives the SPID)