In iOS8, this problem can be fixed.
You CAN recover a deleted photo.
How to recover a deleted photo:
Open your Photos app.
Tap on Albums.
Scroll to find “Recently Deleted”
Open that album and you will see all the photos that you have deleted over the last (approximately) 30 days.
Each photo will have a number under it, telling you how many days are left until it is permanently deleted.
Choose the photo you want to un-delete, and look down at the bottom of the screen. Tap “Recover” to bring your photo back to your photo stash.
All done! No more “oops”. 🙂