They would see the abnormal discoloration of your body, they would look at your age and state of health, and very quickly determine it was not natural. After that an autopsy (which is mandated in most places in cases of unnatural death) would quickly reveal methemoglobinemia and the toxicology report and stomach contents would reveal it was SN. And no one accidentally ends up with lethal levels of SN in them. It's also becoming more and more widely known as a suicide method in the medical field. No one would look at a relatively young person in an even moderate state of health and just accept that they died. And again, your body would be unnaturally colored due to cyanosis. Everybody goes pale after death, but SN causes an unnaturally blue/grey tone to the body.