Quite awhile ago Flash started "deleting" the file in /tmp as soon as it got the file handle. You can still get the file handle using 'lsof' while the video is

Quite awhile ago Flash started "deleting" the file in /tmp as soon as it got the file handle. You can still get the file handle using 'lsof' while the video is playing. It would be easier to just use a tool like youtube-dl or clive (or a browser extension) to grab the videos, though.