I had the reverse happen on the weekend. Went to a historic car rally and got all prepared by taking my pinhole cameras (and associated junk, changing bag, pkts of paper). Had visions of capturing a old car or such... couldn't find one in a setting worth wasting a sheet of paper on! There were people everywhere! I ended up taking some 35mm with 28mm lens (to get in front of the crowds) and some sneakycam candid stuff with a little zone-focus compact, but lost the lens cap off that in my travels! Usually I end up somewhere and wish I'd bought a camera.