Roland Barthes was a French literary critic and theorist, and he wrote
Mourning Diary in the late 1970s to cope with the pain of losing his mother after her death. Rose, of course, is not dead, so Little Dog writes her a letter instead of putting his feelings into a diary as Barthes did. Rose and Little Dog clearly don’t have very much money, since they only buy chocolates while shopping. Little Dog’s reference to the deer again relates to memory—the second deer is almost like a memory of the first—and it also harkens to the mounted deer head at the novel’s open.