The answer to the standard question depends on the point of view:
an average urtban dweller: why would you need a folder anyway, let alone one more
a guy: maybe
a preparednes minded guy: not easily
a knife enthusiast: no way
As I'm a guy I know better than commenting on the women's point of view. You may already have found of about your wife's.
Apart from that a standard response says that you didn't bother to think about it. It may be different in your culture but in mine it is often perceived as a way to say "go away and quit bothering me".
I don't think that not sharing isn't a good idea as she's going to find out sooner or later. You should be able to judge the amount of trouble that would mean for you.
You might wish to consider two actions for the future. You could bring along something nice for your wife. And you might really give it a second thought before you comment on her most recent purchase.