In the missed section or the all section?
They're gone completely. Sometimes they work like it should, others it doesn't.
I've noticed it only happens with texts/iMessages. If the phone is locked and I get one, almost all the time after the phone is unlocked when I pull down it's completely gone, even though it hasn't been read. And, if for some reason it stays & I then lock the phone, when I pull down Notification Center it's gone.