UA-25 issue - recording to both stereo channels with a single mono input?

When recording with a mic through the XLR/phone inputs it sends a mono signal either to the left or right channel.  So in my recording app I get a stereo signal with sound on just one channel.  If I record to a mono track it only picks up the left input, not the right.  If I record through the right input I have to record to a stereo track which has nothing on the left channel.  Is this normal?  If so, what do people generally do to incorporate a mono recording into a stereo mix.  And what do you you do with a guitar track recorded throuh the right input?  This seems strange to me.  My sound card has a 1/4 inch mic input that records to stereo from a mono plug.  I have been using Adobe Audition 1.5 and 3.  I also have sonar 6 but haven't used it in awhile.