Due to an unfortunate circumstance beyond my control, I will not be able to
attend the conference. All airline tickets to the hosting city have been
sold out despite my effort to reserve a seat a month prior to the day of the
conference. Please accept my deepest apologies and inform me of the
key hightlights from the conference.
which sounds like a big lie, I might add. If you really want to attend, you
can try for a standby.