How to un-crop a photo?

iPhoto is so maddening sometimes!

I was cropping a photo for printing, and then intended to send it back to its original size after printing by doing Edit->Undo Crop like it says to do in iPhoto Help. So I cropped it, printed it, and BOOM! I go to Edit, and I cannot uncrop it!

Apparently once you print an edited photo, you can't un-do the edits.

Anybody have any advice on how I can go back to the photo's original uncropped size?