Rebecca,
Three comparables are not required. You mentioned a nearby sale, but I am not sure if that was a vacant lot sale or what you were referring to. Say for instance your house is a one story and the neighboring house is a big two story, they may not be comparable. However, if it is the only sale in the area, I would still think that the appraiser maybe utilized it or at least considered it in some sort.
The industry standard is three comparables. I work in a rural area with unique properties as well. Sometimes I have one "good" comparable, meaning similar acreage size, similar square footage, year built, condition, etc, and then I may include anywhere from 2 to 7 additional comparables supporting various aspects of the appraisal. So, most appraisers will use at least three comparables, but that does not mean that each comparable has to be exactly the same as yours. We can and do adjust for differences.
I agree with some of the others prior comments. Lender selection is a major factor. If you are working with a big bank, they are reviewing this somewhere far from your locale and they do not understand the proeprty and/or the area.
Good luck.