what else would it be? a win suddenly changes to no contest. and unless i'm wrong I think fines and suspensions are public. if a fight result was changed, the reason is always made public. like if it was an illegal eye poke that the ref just didn't see and it led to a fighter being tko'd or whatever. that fighter can file an appeal and the case would get reviewed and the fighter can get the fight result changed. but there'd be no reason to not have that be public.
I can see hiding it if a failed test was known before the fight happens and the fight is cancelled. then they can say it was a medical reason. but even then it would look shady as hell because when fights are cancelled it's usually due to an injury that is made public. if a fight is just cancelled for unknown reasons it's likely a failed drug test.
of course it's a negative perception. but time will go by and the sport will move on. like they have in the Olympics, boxing, baseball, etc. the sport will go on
in jones' case, first of all, banned substances are separated into three groups. one group is banned in-competition. in-competition I believe is like day before the fight, day of the fight and day after. (I could be wrong on the exact specifics of the window) Another group of banned substances is banned in-competition but not banned out of competition. out of competition is basically a certain amount of time outside of what is considered "in-competition." then there is the group of banned substances that is banned any time. and that's the steroids and human growth hormones and stuff like that.
what jones' was caught with was a substance that isn't on the banned substance list out of competition. so the athletic commission can't do anything to him or his record or the fight result. the ufc can do whatever they want with the failed test news within the company. they can strip him of the title, they can fine him or whatever. even let him go if they wanted to. but that's all they can do. they can't keep him, but not allow him to fight. they'd get a lawsuit for that