KTXR was located at 101.5 until '92. The welcome mats in the offices at 3000 E Chestnut still say "KTXR 101.5." As for why they moved, it was because of one of my former employers. Columbia, MO was the largest city to have all class A radio stations. KARO 101.7's owners took that to the FCC as smaller market stations were being allowed to upgrade. KARO, however, could not upgrade at 101.7 because of short spacing issues with other stations (like KLPW-FM in Union). Moving KLPW-FM was going to be impossible because it was too close to St. Louis. So, Al Germond, owner of KARO and engineer by trade, came up with the idea of moving KARO to 101.5, which would require KTXR to be moved to 101.3. The FCC went for the idea, and the rest is history.
I heard the story from Al Germond and Dave Baugher, the former owners of KARO (now KPLA), at a company celebration nearly 20 years after KARO signed on the air for the first time. I've also heard from several sources that Ken Meyer has never forgiven Germond for forcing him to move KTXR, something he fought tooth and nail.