Fortunately, I had a copy of the thread, my practice log. But, how is it possible to recover it from the system? 

Hmm I've asked Simon before and he said deleted stuff is unrecoverable. But did you click "Delete Thread" or you just deleted the top post? If you just delete a post it shouldn't delete the whole thread.. and you shouldn't be able to delete other people's posts if they were in your thread, I don't think.

I'll second Beomans question and ask how did you go about deleting the thread? Deleting single posts is unrecoverable but that doesn't remove the whole thread (unless perhaps it was a single post thread?). Deleting an entire thread is recoverable, but I checked the deleted threads and didn't find one from you.

Simon

Thanks for your help. My thread is "Pablo's Zen/Taoist Practice Log", and you won't find it in the Practice Logs section. Please see attachment below. 

How it happened? As any new post was added as a reply to the previous, after nearly 30 posts the identation was reaching the right side, so I made a reply to the original first post of the thread. After posting it, I tried to edit the fonts but didn't manage to, so I decided to delete the entire entry and post it again. But when I delete that post, the whole thread dissapeared. 

If it's impossible to recovery it, don't worry, I'll re-enter the whole thread.

The thread is still available, see this link.

Thanks Beoman, it must be the refresh of my PC then. Still know when when I look at My Posts, the thread has vanished. I'll reboot the computer, and everything will be alright. Thanks again.