How odd. Over in the PC side of things, Camtasia never actually deletes anything.
I suppose this begs the question. Did Camtasia actually delete the recording from the storage disk? Or did it simply remove the recording from the Media Bin or the Timeline? And if that's the case, it should be easy to add it back to the Media Bin for use again.
The Camtasia app does not delete files, it just deletes items from the media bin. So if you track down where Camtasia is saving your screen recordings, all the files are probably right there.
In case something weird did indeed happen, you of course use Time Machine to back up your hard disk automatically, so you can just recover from that. Now that you can buy an external 1TB drive for $45, you probably have 2-3 backups of everything you've ever done.