Guess what? You discovered p2p spam !
For more on file sizes to stay away from & the typical auto-naming tricking process spammers use, see:
Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see) & check 'all' size examples in both posts to see how they work.
And yes, some spam 'tricks' LW into thinking the file has already been downloaded.