D.C.
Is he really back to normal in terms of his stomach? I'm wondering if his gut flora was wiped out, and he's having some stomach cramps and/or if he's more gassy than usual. From your description, it sounds like he's uncomfortable.
If you think his stomach is still not quite right, you might try some probiotics. My ped always recommended this after any stomach virus (and also after antibiotics). He recommended Culturelle - 1/2 of one adult capsule sprinkled in food for a few days.