I too though of Best on Board this morning when I heard what was written on the sick bag, though I only heard of the term a week or so ago.
I think it a little unfair to criticize some one who may have innocently written B.O.B., be it an F/A, or someone leaving a loved-one behind and doodling. I don't think I would have come up with BOB = Bomb On Board in a month of sundays.