Bob Bennett, executive director of the Nevada Athletic Commission, has come out and stated that Jones shouldn't have been tested for cocaine period. According to Bennett, who spoke to MMAFighting,
That was a bit of an anomaly that will be addressed Jan. 12. It was not a report requested by the NAC. It appears to have been an administrative oversight.
In short - Jones use of cocaine, a drug that can have devastating effects on users, was only caught by chance as the result of an administrative mix-up.