I'm not seeing that cache rebuilding behavior. In my experience, just moving the file to a different folder doesn't rebuild Media Cache or Media Cache Files. It just uses the ones that are there. I can post a screen capture movie showing this behavior from the original location, and new location if need be. Also, cleaning the cache and re-importing shows the same behavior. The clip just doesn't import from its original location--but if I move it to a different location, it imports fine.
Maybe what I should have said is "Very odd behavior--user experience wise". The clip imported just fine in the past (I think that was in CS5.5), from that exact location, and now does not.