Under Office 2010 the outlook file is usually located in you Documents folder inside Outlook Files (assuming your using Windows 7). Provided you havent attempted to reinstall outlook, or create a new pst file in that location you could use one of the many file recovery applications out there to try and recover it.

Avoid doing anything with Outlook if you havent already and look for a file undelete program, I use a program called Stella Phoenix which is a commerical product for such times when my customers randomly delete their wrong files or hard disk failures.

I'm not sure of the rules on posting links to other sites so ive not posted it but you can pm me for it if you want, but a simple google search will bring it up.

Hope this helps, and good luck.