Lost pst folder

I have recently upgraded from Outlook 2003 to 2007. I have noticed on 2 or 3
occasions an outlook message to the effect that outlook was checking the data
file because something had not gone right, eg outlook had not shut down
properly. I can't remember the exact messages because I wasn't aware of any
problems at the time, but I know that I have always shut outlook down
properly myself ... outlook itself might have done something wrong though!

Anyway, now I notice that my most recently created local folder has
"disappeared". Outlook may have erased it as part of its "repair work" or
made it invisible. Has anyone experienced these symptoms before? Is there any
chance of finding/retrieving the emails that were in the folder that has gone
missing please? TIA .... Greg