I hadn't heard this term before until a recent article in the Vancouver Sun. It looks like they are going to save this one. These advertisements on buildings were a part of the landscape as much as the mountains when we were growing up.
Until recently, Vancouver’s oldest ghost sign was for the Louvre Saloon, which operated at 325 Carrall in Gastown between 1898 and 1904. It read “The Louvre Saloon” on top, and “bath house up the hall and beds, 20¢” on the bottom.
But the city has no policy to save old signs, and it was taken down during a redevelopment at the site. The city also did nothing to save a painted sign for a 1922 Harold Lloyd movie, Grandma’s Boy, that reappeared when a building was torn down at Robson and Granville in 2012."
Another one I picked up on an image search for "ghost signs".