Board Thread:General Discussion/@comment-Catharticspurious-20170410011853/@comment-Broken mirrors-20170411083304
Actually, it's a real thing for him. It also crops up in Silence in the Library, and it's the part of the Weeping Angels he seems to find most scary, that they don't kill you but instead make you lost, permanently.
If you wanted to type up 14 volumes of pop-sociology about the subject, you could probably draw a link between Moffat's obsession with memory to his obsession with being lost. I don't feel up to it myself.