Finder doesn't find new excel files
I run an online business and we store customer information in Excel files (Office for Mac 2011). When I search for names in finder, it only shows the files from 2011 or older. New Excel sheets (one is created each day for the days orders) are not found. I have one open right now with the name Trevor Alin. When I search Trevor Alin in Finder, it returns only an old sheet from 2011, it won't show todays file. The same is true for files from months ago.
Is there anything I can do to ensure finder searches new excel files?
MacBook Air, OS X Mavericks (10.9)