The subject of this thread is a good topic of discussion for appraisers to consider.
In the commercial arena, it would be automatic to look at neighboring properties, consider what they are being used for (or, if vacant, what it could be used for) and describe that in the report. I'm doing a commercial report right now (retrospective); the subject is a retail center (small, non-anchored) at the edge of the commercial development and is surrounded by non-retail uses (light industrial; almost exclusively used for auto repair). Although on a busy street, it has limited access from only one direction of traffic. It is not a good location for retail.
Across the street is a new medium-density residential project going up; on the surface, that sounds like a potential positive for my subject (although there is no crosswalk to get to my side of the street, and the walk is about 1-2 blocks one-way by using the existing intersections). However, the project, while predominantly residential, is mixed-use with retail space as part of the plan. This is an inferior retail space to begin with and the new retail space coming online will likely diminish or negate any benefits of the additional housing units. The point is, as of the date of my appraisal, this project was already approved and was going forward even though the lot was still vacant at that time. I don't have to go into a huge market study to analyze the the influence for my assignment. But I do need to comment on what was planned for that space and I can provide an opinion as to its impact on my subject.
It should be automatic, in a residential assignment, if the subject is adjacent to or across the street from unimproved land, for the appraiser to make some inquiry as to what that land is zoned for and if anything is planned for that land in the near future. One would think that if the appraiser has researched the subject's zoning using a zoning map, the land use pattern surrounding the subject would be identified. If my subject backs to something other than what my subject's zoning allows, I should (at a minimum) identify that characteristic and do some minimal investigation to determine if anything is being planned for that space.
One of the problems we have (I include myself here) is that we get set in our routine. If the majority of our assignments are residential properties surrounded by similar residential properties in a zoning that only allows our kind of improvement, it is easy to not worry about land use patterns and if our subject may be influenced by what can occur (why should we worry in that situation?).
A very simple way to change the routine which would help catch a situation like the OP's circumstance is to get in the habit of describing the properties that surround our subject (and would have a significant location-external impact on our subject).
"The subject's site is an interior lot located on the west side of Mockingbird Lane. Mockingbird Lane is a typical residential street within this neighborhood. The subject's neighbors (side and rear, and across the street) are similar residential homes within the same zoning district."
That should be in the site description (along with whatever else is important). By making this part of one's routine, one should never fail to consider proximate unimproved land or zoning differences that could impact the analysis.
Even if the report failed to do anything else, at a minimum, it identified what exists and an argument becomes, "Should more have been done?" rather than "The report failed to identify and consider...".
EDIT TO ADD: I was typing while Howard posted. I think he and I are saying the same thing. Naturally, he says it in fewer words.