Why didn't Ole Andreson show up for dinner on the night the killers were waiting for him?

"I guess I left as much out of 'The Killers' as any story I ever wrote. Left out the whole city of Chicago."
A. E. Hotchner, Papa Hemingway

Because Ernest Hemingway left so much information out of "The Killers," the story leaves many questions in the intelligent reader's mind. It is possible to deduce answers from information provided. Ole is a big man. He has been on the lam for some time and must be working for a living. Since he is not well educated, he must do manual labor. We can assume he has little money because of where he lives and where he eats.
The reader observes most of the action from inside the diner. Business is very slow. If Max and Al had not showed up, the only customers would have been Nick Adams, a street-car motorman whom George turned away in obedience to orders, a man who ordered a ham-and-egg sandwich "to go," and the other man who was turned away and asked angrily, "Why the hell don't you get another cook?" Nick is probably only drinking a cup of coffee on the house. Max and Al do not pay. The only money George collects in about two hours is for the sandwich "to go," which in those days would cost about twenty-five cents.
The streets outside seem deserted. It must be a Sunday night. Ole comes for dinner every night at six o'clock "when he comes," but he does not come that night because he is not hungry. He works hard all week and arrives as soon as the dinner is available at six o'clock. This would include on Saturday evenings because men commonly worked six days a week. Max and Al seem sure Ole comes every night at six, but George says he only comes at six if he comes at all. George may not have noticed that the nights when Ole does not come are usually Sunday nights. The big Swede is not hungry because he has been doing nothing but lying on his bed, the way Nick finds him when he comes to warn him—further proof it is Sunday.
This explains why Ole did not arrive. Many other questions may be answered through logical deduction, and it seems likely that Hemingway expected intelligent readers to seek those answers, rather than supinely assuming the answers are unimportant because the author did not provide them. For example: Why did the killers believe Ole came every night at six? Somebody must have told them. Undoubtedly it was the "friend" they were doing a favor for by murdering Ole—and probably murdering George, Nick, and Sam to eliminate witnesses. But then what made this "friend" believe that Ole came to the diner every night at six, when the plain fact was that he did come at six but not every night? Somebody must have given erroneous information to the "friend." But who? It must have been somebody in Summit. But who? The answer may be found in the fourth or fifth dimension:
The kind of writing that can be done. How far prose can be carried if any one is serious enough and has luck. There is a fourth and fifth dimension that can be gotten.
Ernest Hemingway, Green Hills of Africa