Unfortuanalty, the IRS is the only place that can help you get a copy of the letter that was sent to you. They are the only ones that know about the correspondence. For help with IRS letters, please click the link below. Please note that in order to get any assistance from support, they are going to need you to get a replacement copy of the letter that was erroneously thrown out. The IRS contact options information is contained in the link below also.
https://support.turbotax.intuit.com/irs-notice/audit-support/
