Yesterday I set up Thunderbird: created a new IMAP profile, got messages from the server (no big deal, about 400 messages), archived some of them and moved to Junk some of them, leaving only 3 in Inbox.
Today, I open Thunderbird, press Get Messages, then a dialog asks me if I want to have folders compacted, I press Yes, then I press Get Messages again. I get no new messages, but all seems fine. A few seconds later, as I was actually reading one of the 3 messages in Inbox, most of messages are gone: all 3 in Inbox, all in Junk and most in Archives. In archives, remain a few, and, curiously, these seem to be the first messages I archived.
I checked the server (webmail), the situation is the same there. Synchronization is on.
I am afraid, as it seems, Thunderbird mistakenly deleted my mail.
I am clueless. What could have happened? What can I do to try to recover my messages that are gone? How can I do prevent this problem from happening again?