Surely, for the faulty transaction to still be in the log file, the database must be in full (or bulk-logged) recovery, so you ought to be able to do a point in time restore to before the oops moment? In simple recovery the transaction could well have already been overwritten in the logs when you come to look at it, and if you're in full recovery and not taking regular log backups...well, I don't think I need to elaborate on the problems there!