The data when you copy and paste something such as a photo or text is saved to the clipboard on your computer.
That clipboard on your computer is basically in your RAM where the data such as the pictures and text are temporarily saved.
So when you copy something it saves to your RAM stick and then when you copy something else that data is deleted to make room for the new data.
So every time you copy something and then copy another the old photo is deleted to make room for the new one.
So if you copy something to your clipboard you need to paste it and save it as soon as possible in case you forget to save the information to your hard drive.