ask the community – Security Code

On 08-17-13 I logged into Outlook, but before I got to the actual emails, I was prompted to make a selection.  I selected my landline to receive the security code.  I was called right away with the code by an automated system.  I entered the code and was then able to proceed to my Outlook mail account.  My first thought was that the request had something to do with not being able to access mail at all on 08-14-13 (one day).  However, later, I was worried that perhaps my account had been hacked by entering the code and did a reverse lookup on the phone number that called me.  The report I got did not show the number as belonging to Microsoft; all it said was that it was associated with heavy spam activities.  I sent a secure e-form request 46 hours ago but no response yet.  Can anyone please give me any info on how I might determine that the "caller" was legit?