There are a number of levels at which we can discuss what's not shown on the map of Purdue in the phonebook and why. At one level, we can look at the representation of departments and programs. Certain buildings that are "officially" part of Purdue's West Lafayette campus are not shown because they are too far away to be easily shown, or because visitors to campus would not normally visit them. The politics of program status also affects what is shown on an official map, with larger (and more well funded) programs being granted status in the legend, which indexes a list of programs, departments, and buildings alphabetically with the spatial map. If a program is large enough to warrant an entire building, it will be mapped here by default.
At another level, we can look at the urban geography of West Lafayette. There is little on the map to indicate where the city itself lies (just East and North of campus, off the map). Residential streets are shown where they jut into campus, but the names of these side streets are not given on labels. The campus is isolated from the city, in cartographic if not social terms.
At a broader level, the phone book itself contains separated listings for students and faculty/staff, to enforce the differential status of each group. (It's a wonder that groups within each of those haven't succeeded in hierarchizing their own listings, perhaps with faculty separated from staff, or grad students insisting on a separate directory from the undergrads, etc.)
At another level, we can ask about the location of violent crimes on campus? Where can we get a map that shows muggings, rapes and attempted rapes, sexual harassment, racist graffitti and flyers? This listing might be more instrumental in solving the problem that emergency phones address--avoiding violent crimes.
But avoiding crime was only part of the message. The image of safety was another.
I want to avoid saying that the mapmaker acted irresponsibly, because -- like the mapmaker -- I am forced to leave much out and cannot say what additional constraints the mapmaker worked under.