My husband and I have definately had times/restaurants where one or the other of us (never both at the same time!) have had this happen. We try again another time before we decide we don't like "that" restaurant because one of us has a problem with it.

There's so many things that could be causing it; the particular restaurant, what's eaten, one's mood before/after, etc.

Is he on any meds? My Synthroid was too high and that was causing me problems. Some meds accelerate the intestinal tract and maybe with "restaurant food" or how it's prepared, that would do it all the time for him.