After the flash version 10 as I can remember, the old method of going to the temp folder /tmp/ and copying the video from there is not working, you will not find it there, It is put there then deleted from disk and treated as a file in memory so this is how to get it.
Using the terminal:
pgrep -f flashplayer
this will display the process IDs using flash player, assume the process ID was 3660, then navigate to the process data
and list the files there
you might find a file written at the end of its line ” /tmp/FlashXX3HWsv1 (deleted)”
this is the video, copy it to wherever you want but use that number as the file name
cp 30 /wherever/vid.flv