How big it the 'big sister' ? Maybe you need to have a x ray taken to made sure your dog did not get hurt internally . If you use canned pumpkin made sure it's not a 'pie filling ' this will have sugar and spices in it which will not be good for a dog. And I thought pumpkin was fed to dogs when they had loss stools.
http://www.wikihow.com/Treat-Dog-Diarrhea