It's a toss-up whether symbol or theme is third. Symbols are figures of speech which have a value in themselves, but also an additional meaning. A flag is a nice piece of patterned cloth which can decorate a wall or hang on a pole outside somewhere. It also can be symbolic of patriotism. An escape story supplies a surprise ending more often than interpretive stories do.
Happy endings are nice, but indeterminate endings are more like real life.
Happy endings may be satisfying, but they do not make readers think. Chronological order may be convenient, but it is not always the best order for a story. On the other hand, manipulating the events and outcome of a story is very high-handed. . Stories which end like this have indeterminate endings. When I started reading these stories for the first time, I wondered how I could keep the characters straight, and remember the authors and titles.