Very entertaining thread for a boring afternoon here
... sorry.
But honestly, using your desktop to store a library? to store anything you don't want to lose? That's just begging for a disaster to happen.
Calibre is a super program. It didn't need the extra confirmations that Kovid did to try to appease the OP, yet he did it anyway. The manner it deleted the library was exactly the same manner every other program will delete its files... they never move them to the recycle bin, the program deletes the files.
I just had a problem a few weeks ago where trying to switch profiles in Thunderbird ended up with it deleting not what I intended. It was entirely my own fault for not simply taking 2 minutes to put a full copy of the emails at least elsewhere before I started tampering with profiles. But yes, it deleted the entire profile, files were not in the recycle bin at all, as any program will do. Instead of yelling at Mozilla, I ran a data recovery program and got most of the old information back. There were some emails I really didn't want to lose from the last several months that I needed. It took a little time, but most everything was restored.
Again, it was clearly my fault in just doing something hastily (and stupidly) without thinking. As it was clearly the OP's fault here as well. Bashing the program isn't going to get your files back. Start looking into data recovery, there's some good free programs out there. Just do not install the program to the drive you want to recover data from, do not even save any documents to that drive, leave it untouched, and you should be able to recover virtually all of your files.
Thank you, Kovid, for an outstanding program that I couldn't live without at this point, and all the constant improvements you keep making to it.