The trash can (US)/rubbish bin (UK) is at ~/.local/share/Trash and doesn't exist if you've never put anything into.
Adding it back through Déjà Dup's GUI requires right-clicking in the dialog box to select Show Hidden Files and get into .local, otherwise from the command line you can run
$ gsettings get org.gnome.DejaDup exclude-list
to print your current excludes and then
$ gsettings set org.gnome.DejaDup exclude-list "[<your current excludes>, '\$TRASH']"
So not a bug, although not obvious when you don't know where the trash is.
The trash can (US)/rubbish bin (UK) is at ~/.local/ share/Trash and doesn't exist if you've never put anything into.
Adding it back through Déjà Dup's GUI requires right-clicking in the dialog box to select Show Hidden Files and get into .local, otherwise from the command line you can run
$ gsettings get org.gnome.DejaDup exclude-list
to print your current excludes and then
$ gsettings set org.gnome.DejaDup exclude-list "[<your current excludes>, '\$TRASH']"
So not a bug, although not obvious when you don't know where the trash is.