That's why they spin - to distribute the enormous heat. They would also leave behind a shock wave wake that would be a bit of a give away.
Coincidentally blurred pictures of chrome hub caps thrown like a frisbee seemed to sell newspapers in the 1960's. Shades of B movies like "Plan 9 from Outer Space" and a better example "The Day the Earth Stood Still".
In the latter case the original was way better put together with the limited special effects they had than the much later colour remake.
USA had a UFO tourist industry centred around Roswell along the exactly same lines as the Loch Ness monster.