Using Windows Live Mail 2012 and Windows 10 on a PC

After successfully using Categories (groups) to send emails to a list of folks, suddenly the several Categories have disappeared. I think some of the email addresses in those Categories have also disappeared. Some of the Contacts are still there, some are not. So now I have to not only create new Categories but also figure out which addresses have disappeared from my Contacts list so I can re-enter them. I suspect the missing Contacts are those that I created as I created the Category. It's been a number of months since I installed Windows 10, and the Categories have been there until a couple of weeks ago.

Is there any way to retrieve the Categories that are gone? If I go through the trouble of re-creating the Categories and re-entering the Contacts, will they still be there in a few days or weeks?