Sounds likely your antivirus is removing the files, from a reputation/general false positive (based on other posts vouching for download linked material being ok).It's really weird but when I tried to copy it and put it into the packs folder (on the game folder) it just automatically deletes itself. I don't know why because when I set it up the first time it worked but now it just automatically deletes the files (that weren't already on the game pack)
If you trust the files, create an exemption using your antivirus software, either for the whole folder you're installing into, or for each individual filename using the folder and filename. AFTER creating that, then copy into the packs folder.
I've done this on other games with my AVG Free program.