My parents have an old "Red" hymnal at home, with many of the Saints days in them. My grandfather's worship book has most of those and a few more (don't know enough German to be sure on some of the names).
It wasn't that they weren't on the calendar, but that for a long time they were "forgotten".
The Apostles' Days first appeared the Common Service Book of the United Lutheran Church (antecedant to Lutheran Church in America and ELCA) in 1913.
There was a decent level of awareness of these days because these were permitted to celebrated on Sundays other than Sundays in Advent, Lent, or Easter. That Lutheran peculiarity suddenly became a source of embarassment so the new ELCA hymnal actively discourages (but does not forbid) that practice on the basis of "ecumenical practice".
I don't know that much about the Missouri practice except that Sunday observance had not been permitted in Lutheran Worship but now is permitted for a few Minor Festivals, such as the Presentation and the Nativity of St. John the Baptist.
In some parts of Germany and Scandanavia there was so great an appreciation for the "six great festivals" (Presentation, Annunciation, Nativity of John the Baptist, Transfiguration, St. Michael, and All Saints) that these became regarded much like the Roman Catholic "holy Day of Obligation" on which attendance at the services of the church was pretty much expected. Of course that was one of many casualties in crossing the Atlantic.