Lost my mail

I recently decided to "clean out" my in-box.  I created a new folder that I titled "Archive" and did a drag and drop of older emails to that box.  The computer acknowledged the move (or copying) and those emails showed up in the box.  I just (several days later) opened the box, and only one email appears.  I checked properties and it says that only 1 file is on my computer and 1 file is on the server (Microsoft Exchange).  Have I lost everything?  If not, where do I look to find the older mail?

thanks