Newly Migrated Email Folders Have Disappeared!

I have recently returned to Outlook for Mac 2011 after about a year of trying Apple Mail and then Postbox. I am using version 14.4.8 with the latest version of Mavericks; provider is AT&T. I use 3 different email accounts. all Imap.

I spent all last weekend migrating over 50 mbox folders using Stellar Mail Converter. A few folders were already Archive Folders, and I left them as they were. The rest I put under "STORAGE FOLDERS" under "ON MY COMPUTER" Everything was fine until yesterday when I first opened Outlook and discovered all my folders were gone! I first looked in the obvious place, "TRASH". but they were not there.

I have not made any changes  in the Microsoft User Data folder or done anything with Identities. There are actually 2 identities, the second having been modified on 3-17-15, which was when I actually finished  the migration to Outlook from Postbox. I have no idea WHERE or  HOW to look in either identity to determine if my migrated files are actually there, much less whether it i even possible to do so. Of course, I still have all my Postbox .mbox folders I can migrate again, but I don't want to do that without figuring out WHY they disappeared!

This has been very frustrating, needless to say, so I hope ya'll will have some answers as to why this happened, as well as what my next step should be.

Thanks so much,

Pat