Wow! Twice I stated that I am still able to select Save Image, and both times you tell me "Yes, it is still possible to do this."
Is English your primary language?
Dragging the app preview up away from the display at the bottom of the screen accomplished nothing. Yahoo Mail is still there when I go back to the regular layout - it's the mail app below the main screen and is right next to Safari, Photos and Music. I did not want to have to delete the app and then reinstall it, but apparently that may be my only recourse.
If this problem were on my Mac Pro, I would restart Yahoo Mail. If that failed to correct the problem, I would restart my machine.