Causes “hidden” images in iPhoto album to reappear

I made a few edits with the program to a photo. Easy enough to use, but not necessarily much different than Aperature. I exported from Intensify to iPhoto. Once in iPhoto, I pulled the single image back to the album for that event. Once I did, all hidden photos within that album appeared. I was able to undo the merge. But not happy with this outcome.

Yzsutty about Intensify