Me thinks said author is a clueless bafoon, who knows squat about gun ownership in MO. I've never had to "register" any firearm I've bought (assuming I've ever bought one), whether it was through an FFL or a private sale. I did have to get a CCW license pre universal CCW, which passed 3 or so years ago.
Maybe the author knows of some secret program that allows people to voluntarily pre-confiscation "register" their guns in order to make the government's job easier?
Of course we hear it on tv crime shows quite frequently.