Mysql disaster recovery

2 hours and no answers? I think that could just be because nobody is willing to break the news to you.

Do you have a good copy of the data anywhere at all (even one that's a month or two old)? If no, then you're SOL I'm afraid. You've made some allusions to a synchronised copy of the database, so if the synchronisation was taken down before the bad UPDATE statement was executed, you will need to create a statement to update Source A with Source B's data for that table.

(I had this once, with MSSQL and log shipping, and thankfully was able to stop the log shipping before the bad data was restored on Site B, and just did an UPDATE statement between the servers to undo my mistake).

As Marc B mentioned, if you have binary logging enabled (and the log hasn't been truncated) you might be able to recover some of the data by getting that log to be replayed (even if you have a reallllly old copy of the database, if your log is intact you'll be OK), but that can be a bit hit-and-miss.