Why did such a bug ever make it past the audit stage? unless there was
1) no audit beyond initial copy and paste, (he team lacked the competence to notice such a trivial un-optimization)
I guess you were volunteering to audit the tens of thousands of lines of code with no design documentation and no comments?
For that matter, if you are still volunteering to do this, we have openings, since the process is ongoing.
No one knows for sure when they found out.
The file was named "slow-hash.c". The file name itself says what it does. The bytecoin devs had optimized miners from launch until the crippling was found.