We have relatives visiting this week (which accounts for this issue being a day early), so please don't expect quick email replies for a few days. [ACE]
Find Photos in iPhoto in the Finder
Looking for the file associated with a photo in iPhoto? In iPhoto, to view a photo's file in the Finder, Control-click it and choose Show File from the contextual menu that appears. You can then drag the file's icon into an Open dialog to upload it to a photo-sharing service, for instance, but whatever you do, don't move or rename that file!