It's passed by other dogs in the feces. They can pick it up off the ground or anywhere. Was your pup vaccinated? (puppy shots?) Your dog may have worms which can cause diahhrea or it could be the food just doesn't work well. I'd do the pumpkin and perhaps some live culture yogart...just a couple teaspoons at first. But human diahhrea medicine, I found out from the pharmacist isn't the same compound that it use to be. It may be that this stuff would irritate the lining of the intestines. This is what the pharmacist told me when I asked about Kaopectate. The vet had recommended a little of that for my dog when he had problems and when I asked the pharmacisit about it, that's when he told me that they had changed the formula. So, I'd be careful about using medications. Also, I agree that giving bones would be dangerous.
Boiled chicken and rice is plain and normally easily digested. Rice tends to firm up stools. It is helpful with diahhrea. But don't use Minute rice. It has to be real, sticky rice. It is not very fibrous, so it won't increase the bulk of the stool, but to get the diahhrea under control, that can help, along with the pumpkin. I'd try that for a few days and see. But if your dog has worms or some other illness, that will not cure it, only help with the symptoms.
Tell your parents that everyone on the message board thinks that your dog should see a vet. Diahhrea that goes on and on is an indication that something is wrong. It can also, if allowed to go on for a long time cause long term, permenant damage to the intestinal lining, which can lead to some cancers.
I wish you all the best.