Do you know where your original IRS application for exempt status is located?  Do you need a copy for your records?   Do not fear the IRS can help.  You can file a Form 4506A Request for Public Inspection or Copy of Exempt or Political Organization IRS Form.  You can find this form at the IRS's website http://www.irs.gov/pub/irs-pdf/f4506a.pdf.

The form is fairly straightforward (at least from my accountant's point of view).  When completing the form just add the following to the Line 5 Reason for Request:

"We need a copy of the original determination letter and Form 1023 for the organization's permanent file."

Make sure to check the boxes in Line 6 "Form 1023" and "Copy". 

We recommend that you have a copy of your Form 1023 and IRS Determination Letter in your permanent file.  The IRS granted your organization exemption based on the information you provided in your application.  It is your responsibility to notify the IRS of any changes that you make as your organization develops.   You can report minor changes on your annual Form 990.  Significant changes need to be addressed with the IRS before they occur.  Make sure to contact your CPA if you need to report significant changes to the IRS.