Minding My Own "Business"

Minding my own business, when we get a phone call from an old customer who insists that we find an invoice for him from 1991.  WHAT!  First I wasn't at the office when the call came in so this is what I have to deal with when I go back into the office.  Second, we have records, online records from 1999, before that it was strictly all handwritten by my itty-bitty hands.  Those records probably don't exist anymore, I think they have been shredded.  If they are still in storage they are upstairs in mouse and silverfish laden boxes that I DON'T want to go through.  I mean really, 21 years later he wants us to track down an invoice.  The Hubby may have to shut this guy down.  Can you tell I'm a bit agitated!  Common sense tells you that a company will not have a hard copy invoice from 21 years ago, am I right!