That should be Thursday's feast: the second feast of Our Lady in the New Liturgical Year after the Immaculate Conception. It would be the Mass Rorate with one change, a different last versicle at the Gradual: "Behold, a virgin shall conceive, and bring forth a son, Jesus Christ". A week before Christmas there is an opportunity to reflect on Our Lady's pregnancy and on the physical hardships she endured before Our Lord's birth. But it was reformed out of the Calendar, not by Bugnini, either in his Pius XII or Paul VI periods, but long before.
A lot went wrong liturgically in the twentieth century, before its second half.