sounds like spam of a new size. Try setting it as junk.

It was already set as Junk... spam ayy
every subject I search for in the found results the same 3462kb file has already downloaded.

Unless its something you don't want someone else to stumble across in your PC I'd ignore it when it appears.

I understand the irritation but is it worth a day out of your life to pursue it? I've found such stuff in unlikely places while doing other things and dumped it then.