From the OP's perspective, it does seem odd not to just say, "Yeah, I bought it yesterday."
I may be projecting, but I have done the same thing OP's DH did to my DH. Even if we have the money to buy something and I know it is OK, I still have the tendency to just bring the shopping bag(s) in quietly and put them away without comment. He sees the bill (joint account) so it's not like I am hiding or even trying to hide the purchase. But growing up, my every move and especially every purchase, was scrutinized. My parents still do it. Whenever they see me, they do an inventory, "Oh new shoes? Hmm..." "Did you get your hair done? Hmm..." "I haven't seen that sweater before. . . is it new? Hmm..."
So I avoid bringing attention to my purchases after a lifetime of training. Maybe that's what he was doing?
Or maybe he was so engrossed in his Dexter episode that he doesn't even know what the OP asked him, hence the shrug.