Got the impression you asked this before.
Anyway, videos are stored (very briefly) in a Temp folder (this could be the Windows temp folder, your user's temp folder or a temp folder (hardcoded) by the player that is used on the web site. Most of the time these files have undescriptive names and file name extension.
You'll need to find out where the video file is written on your system. Make sure the video is completely loaded, but before the video has finished playing you should unlock these temporary files and copy/rename them appropriately in a folder of your choosing. Granted, this isn't the easiest way to get videos, but you'll be surprised how much videos you can get this way.
As you report, you want to get flash videos. Now I'm not the only one who thought of this way to "catch" videos. For this reason flash videos are cut into pieces that get downloaded just before the video player in your browser is about to show that part of the video. This makes "catching" videos harder and as an added bonus, it saves bandwidth on both the transmitting/receiving sides (at the cost of viewing experience for the end user who has no or limited access to high-speed internet at any given moment in time).
For Firefox there is a plug-in
YouTube Control Center
with which you are able to change this behavior of the video-player back to the old-fashioned 'all at once'-method of transmitting/receiving video. Not only Youtube videos, but from other sites as well. Armed with that plug-in and unlock software (or shadow copy software) you should be able to "catch" videos again.
With most videos it just isn't worth the effort or time you'll be spending. But the method does work, so if you are dead set on getting this video, it is a way of going about things.