The Idaho Death Certificate Index does not list a Nancy Salinas which opens a couple of possibilities. First is that her death certificate was missed or mis-transcribed in the index. I have not seen this happen more than a couple of times. The second is that no death certificate was filed. That was contrary to the laws, but it happened more often than you might think. I have seen it happen several times in Cassia County and they were all where a person died of natural causes related to old age and were in a rural area of the county. Apparently the family buried the deceased without any involvement of law enforcement or undertakers.
I'd suggest checking all variations of the surname on the byu-Idaho site or reading the local newspaper to see if there is an obituary (which might provide a clue about why no dc). If a death certificate can be shown to exist, the folks at the byu-Idaho site will send you a copy.