What if he hadn't just bought it and they actually had it all along and OP just didn't realize? Would you all still think she shouldn't have expected an answer? (Not snarky, I'm being serious. Would it change your opinions?)
I'm with the OP on this one as far as expecting an answer. It doesn't matter if the conversation is "inane", when someone speaks to me, I respond. Other than noticing his noncommittal shrug, how else was she supposed to know that he heard her? If he doesn't acknowledge that she said anything, even with a simple response, she can't know if he actually heard her. I have to keep explaining this to Dark Boyfriend. If I'm not looking at you and you don't respond, then I don't know that you heard me.
It doesn't have to be in the form of a question to be a question. A statement can imply a question just as easily as a question can be asked.
OP: I'm going to have to with he shrugged because he was too into what he was watching to actually respond. Dark Boyfriend does this...when I notice the glaze go away from his eyes, I say whatever I said again. The shrug, to me, is: I heard you, I don't know what you said, I can only process a shrug right now because I'm trying to follow what's going on. Don't take it too personally.
ETA: Didn't meant to sound snarky.