I know the area your describing, and if there is in fact a floor glyph there, then they are not unique, as I know of at least one other.
Over the next few days I want to start mapping out the locations of the 'simple' glyphs, in order to give us all a better reference to refer to, and to see if there is any sort of pattern to their placement. I will be sure to note the presence of any strangely placed glyphs as well.