iPhoto iPhone photo import cache folder? If I connect an iPhone to my Mac (any iPhone, whether one that is synced with my library or not), iPhoto will open and directly show the photos stored on this iPhone and allows to "Import Selected".

Without selecting any of the pictures, does iPhoto somewhere store the thumbnails that it displays on this screen?

If so, where is this cache folder on OS X?

The reason I'm asking is that I connected a foreign iPhone and iPhoto popped up displaying the photos stored on the device and I want to erase any image data that potentially got transferred to my Mac.
Inside your iPhoto Library is a folder named Caches. This folder contains temporary thumbnails generated in circumstances such as a pending import. You can delete the contents of this directory, although iPhoto should manage it itself.