Lutherans weren't worried about May 21

The secret rapture, where some people are snatched away and others left behind for a second chance, isn't familiar to most Lutherans (or really most Protestant groups), unless maybe they've joined a neighborhood Bible study outside their tradition. The "rapture" is when Jesus returns, the dead in Christ are raised and then immediately comes the judgement of the living and the dead and the reward. See Matthew 24-25. It is also described in 2 Peter:10, but what follows is what is important: "Since everything will be destroyed in this way, what kind of people ought you to be? You ought to live holy and godly lives as you look forward to the day of God and speed its coming. That day will bring about the destruction of the heavens by fire, and the elements will melt in the heat. But in keeping with his promise we are looking forward to a new heaven and a new earth, the home of righteousness . . . so make every effort to be found spotless, blameless and at peace with him. . . "

So, although there were a lot of jokes about May 21 (like what did you pack for the trip), at least a few people probably stopped to think about whether they were ready. In God's economy, nothing is wasted.