Little research has been done thus far on how long salvinorin A stays in the system. After all it is not part of any standardized drug screen, and I do not think that it will ever be.

It would be very hard to look for due to the very low dosage(200 to 500ug). It's effects are also rather short lived.
And despite what the media and political types may say, SD is NOT a new MJ, crack, meth or LSD. These paranoid media morons are just so damn ignorant, or just plain stupid, that they do not know the difference.
On the medical front lines, in the ERs, we do not even see SD related incidents. Alcohol is still the #1 associated with drug overdose and injury.
Stimulants like cocaine and meth are next on the list. Opiates and tranquilizers are next as far as ER related incidents go. DXM, LSD and PCP are rather rare as for ER related incidents, but I've seen those drugs as issues in the ER setting before.