My fiance didn't ask my dad for my hand in marriage before he proposed. We have been together for 6 years and they have a good relationship.

I didn't want to ruin the moment, but when he told me that no one knew about the proposal I was really sad because I have a close relationship with my father and knew that it would hurt his feelings. It's now been 2 months since. Should I ask him why or just let it go?