Ranchgal it seems that Ennis did know that Francine went upstairs judging from the following exchange.
Ellery: So how come Francine don’t want ta stay?”
Ennis: “I don’t think she likes the bar. She acted funny when we went in, wandered around upstairs an then said it was smoky. She probably is havin problems with her asthma again an don’t want ta worry me about it. I used ta have insomnia worryin about Francine’s asthma, an she knows all that, so… don’t press her, all right?”
I guess I didn't read that part carefully enough then, thanks for pointing it out, I still think he has pretty much spaced it off as he wouldn't have thought anyone else was in the bar anyway.
AND the asthma is a good enough excuse---She and Jr seemed to be covering themselves well by then. AND he would figure, if she saw some stranger in the bar--she would have hollared about it, she is kind of flightly anyway. Besides, they will be gone early, according to their plan, and I just don't see it being an issue, but I have been wrong before, and certainly will be again.