Every once and a while, I lose network connectivity to the point where my NFS share is unmounted and, when remounted, the Desktop fills up with everything in ~/.

The problem lies in the file ~/.config/user-dirs.dirs. It should be as follows (for my setup):

XDG_DESKTOP_DIR="$HOME/Desktop"
XDG_DOWNLOAD_DIR="$HOME/Downloads"
XDG_TEMPLATES_DIR="$HOME/Templates"
XDG_PUBLICSHARE_DIR="$HOME/Public"
XDG_DOCUMENTS_DIR="$HOME/Documents"
XDG_MUSIC_DIR="$HOME/Music"
XDG_PICTURES_DIR="$HOME/Pictures"
XDG_VIDEOS_DIR="$HOME/Videos"

So, for example, XDG_DESKTOP_DIR="$HOME/Desktop" when remounted turns into XDG_DESKTOP_DIR="$HOME/", thus the problem. The correction is to replace with the above. I plan to write a script to check for the missing directories after $HOME/ and replace as necessary.