So according to this video, in March of 1981, a building from Columbia is found in the Alps. Which would imply that Columbia was over Europe at some point (maybe not recently though). That got me thinking, if Columbia hadn't crashed or was destroyed by that time or even the late 40's onwards, we should have been able to find the damn thing any time it passed over a major land mass that is watched by a radar system, military or weather related. That thing would have showed up on weather radar like a sore thumb. I remember working a forecasting shift at McConnell AFB, when the Columbia (shuttle) broke up over Texas, and let me tell you that left a very large swath on the radar.