Have your temporary Webkit files disappeared from your /tmp folder? Perhaps you should be looking in your /var/tmp folder instead. Recently Firefox and Safari seem to store flash temporary items in a new location. Look in /var/tmp/folders.501/TemporaryItems. (This assumes that your user id is 501, which is typical but not certain–type id at the command line.) Instead of being named “Webkitplugin”, the file will be called something like “TemporaryFlashItem”.
I was wondering where those files had gone. Thanks for that!
Alternatively, one could use iCab to view such files then use its cache browser to save them.
This really helped. Had some trouble "finding" var/tmp but then used the Finder's "Go To Folder..." dialog to type in the path; that might be a detail to add to the article.