And another thing. While I am agreeing that asking unequivocal questions is a good way to fish information out of someone, you have to be careful, and also not hope that you will get a straight answer out of them Humans may (but not necessarily) play mind games even if they pretend they are giving straight answers to straight questions. The ability to see through does not comes easy :P
This is one of the best scenes which comically illustrates the effort of humans to understand others in their social relations:
This scene may be exaggerated and comical, but in essence this is what we humans do on a daily basis in figuring others socially.Your predicament reminded me of it. Psychology calls it "theory of mind"