Cabbage weevil's post reminded me that publishers often insert fictional places in maps.
The idea is that, if the map is pirated and published elsewhere without permission, the places that don't exist establish the copyright.
There's an interesting thread about matters of this kind -- including "copyright traps" on maps, per the process which you describe, which ultimately became real places -- on the Fortean Times discussion forum.
Log on to www.forteantimes.com.forum/index/php
;under "Specialist Topics" there, click on sub-forum "Urban Legends / Folklore". Page 1 of this sub-forum: about seven items down, thread "Places that don't exist".
Included there, is the strange tale of the supposed Sandy Island -- allegedly several hundred miles east of Australia, and measuring fifteen miles by three. It was recently found that this "island", which has featured on maps for quite a long time, actually doesn't exist. Discussion is generated thereby, as to whether it was a copyright trap gone wrong; or pure human error; or whether at the island's alleged discovery in the 1870s, it was a sandbar then existing, but subsequently covered by the sea; or something else?
Deliberate distortion of, and putting wrong info on, maps for the use of the public happened rather a lot in the former Soviet Union; this being done at the behest of the authorities, to thwart would-be spies. It was maddening for local citizens and (blameless) foreigners, who were just seeking to get to where they wanted to go. As regards the USSR, one feels that the kindest possible verdict is "they were a funny lot".