Hi there and welcome to Just answer!! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
From what you have told me, it appears that Sampson has a mild digestive disturbance. This could be from something that was eaten or from some type of stress. The best thing to do for this is to fast him for 24 hrs. This allows the digestive tract to calm down and heal. Also, give him Pepto Bismol at 1 teaspoon per 20 pounds of weight every 8 hrs. After the fast, feed a meal of boiled chicken and rice. If the disturbance has resolved, wean Sampson back onto the regular food over 2 days.
It is extremely important that if Sampson continues to vomit during the fast, that you have him seen by a vet immediately. Even the dehydration will causes severe problems for your guy and this must be taken care of right away.
If Sampson is still having difficulties, you will need a veterinary exam to be sure we have not missed something. This disturbance could be more severe such as an intestinal obstruction or other infectious agent or a pancreatitis..
Good Luck! Sincerely, XXXXX XXXXX