I'm Running Windows Live Mail, the 2011 version, under Vista.  This is the WLM mail client, not Outlook Webmail.  I POP/SMTP messages from four different accounts with various providers.

At the top of the WLM page, there is a "Sign In" button.  Hovering over it, a message comes up, "Sign in to Windows Live Mail using your Windows Live ID."  I think the 'Windows Live Mail' they're talking about there is now called Outlook.

I have not used this button since MS dumped Messenger some time ago.  Today, just because I'm stupidly inquisitive, I hit the button and signed into Outlook, just to see what would happen.  Well, at the time it looked like nothing did, but evidently doing that replaced my local WLM Contacts, resident on this computer, with a very old assortment of Contacts from the Web, dating back to when I quit using Messenger.

All is not lost, some of the old ones are still good, but newer contacts are missing completely; that is, neither on the computer nor on Outlook on the Web.  Did the Contacts file on my computer really get wiped, or is it lurking with a nonstandard extension somewhere and might be recovered?  All help much appreciated, thanks.