Windows Live Mail messages completely gone from all accounts and folders

I apologize for any redundancy, but I've been searching the forum for a long time, and the info I found seems to apply to all kinds of different scenarios, but none with the same parameters as mine.  So I'm posting my request for help for my specific situation.

The issue concerns Windows Live Mail on my desktop. (ISP is Earthlink, in case relevant)  WLM has been working just fine.  My husband, who is not computer savvy, was working on the computer earlier today.  The WLM program was open but was minimized. He was looking at various websites on Chrome.  When he was on my desktop after closing a site, a message window popped up saying something about 'unused disk space being recovered'.  It seemed to occur automatically, i.e. he didn't activate it because he's afraid to do anything he doesn't know about.  So he got off the computer at that point.  A bit later, he opened WLM to check emails, and ALL (I mean, EVERY SINGLE ONE) of the messages that had been in the folders of our 4 accounts were GONE!  All folders were still there, but they were all empty. It shows "there are no items in this view."  However, my views are set for "all messages", and I hadn't changed any settings.  I'm trying to figure out what happened, but I'm MAINLY trying to find where all of those emails went.  I know that he could not have deleted the emails, because it would have meant deliberately deleting messages from multiple folders for 4 accounts.  All of the folders are still intact and now have newer emails downloaded in them.  Any suggestions as to what might have happened?.  At this point, I'm hoping that the messages weren't DELETED by the program, but were moved to some other storage location in conjunction with the "unused disk space recovery" activity, and still exist somewhere for restoring to the active folders. 

Other issues::  My email was hacked a few weeks ago, but I changed my password prior to the disappearance of these emails, so I think this shouldn't be related to that.  Also, I wondered if I might have gone over a message limit maximum, but even so, I can't believe that would wipe out all messages in all accounts across the board.

Thanks for any feedback or suggestions that you BRILLIANT experienced users can provide!