Of course there is nothing better than an afternoon picnic, while watching Sydney Harbour change into its swath of Fortuny silk blue for evening, and first walking past this picnic Tuesday at sunset - the champagne bottle down two glasses, the food untouched, the picnickers, were absent, paddling or perhaps one had not arrived, and the jilted party had drunk the second glass and took a huff home?  On Wednesday evening the picnic was - as shown here - still perfect, not picked over by gulls, or blitzed by ibis. By Thursday morning one strawberry and a breadstick had gone.  A photo shoot?  A trap for speculation?  Pnin?