Aww, poor little Sam - I hope he's doing better this evening!
My 2 boys went through similar bouts of the vomiting/diarrhea thing and both times it was because they ate something bad - Kalani ate part of a plastic mat under his x-pen and Pi'i ate some duck poop at the park
Their tummies were real sensitive afterwards so I kept them on bland diets and gave them a dose of Pepcid as needed and eventually was able to get them back to normal.
Will say a prayer for your little one that it's just an upset tummy and that he'll be bouncing around real soon!