Here where I work we received strange emails from those who had us in their address books.  These "worms" are apparently sending emails to everyone in the address book with an attachment containing a virus.  We discovered it when one of our resellers saw about 100 RE: emails, yet he never sent the original to begin with.  So he emailed all of us to warn us and tragedy was averted.  But to answer the original question:  YES, it is possible, and probably likely, that that guy never intentionally sent you a virus.