Waterdeep: Detection and Location Magic

Forgotten Realms Campaign Guide, p. 199:
"One invisible local change wrought by the Spellplague is all too familiar to local spellcasters: Detection and location magic no longer functions. Such spells feature in old tales but are unknown in life today."

I felt like this required a tiny bit of expounding upon. To those trained in Arcana, it is well-known that magical spells and rituals intended to find hiding or missing objects or people in Waterdeep (e.g. Locate Object, Scrying, etc.) fail outright. While some rare, and apparently inconsistent, tiny areas of the City of Splendors may not suffer from this problem, it is widespread enough to discourage very nearly all spellcasters from attempting such things in or under the city. Attempts to locate a fugitive hiding within the city might lead a diviner to the gates, but yield no guidance past that point.