According to IRS - http://www.irs.gov/businesses/small/article/0,,id=108532,00.html
Q. What if I forget the number I obtained over the Internet?A. IRS records will be updated immediately with your EIN. Simply call (800)(NNN) NNN-NNNN/strong> and select EIN from the list of options. Once connected with an IRS employee, tell the assistor you received an EIN from the Internet but can't remember it. The IRS employee will ask the necessary disclosure and security questions prior to providing the number.
If you previously applied for and received an EIN for your business, but have since misplaced it, try any or all of the following actions to locate the number: