One other thing to keep in mind when discussing protein is the human body requires far less protein than people realize. The fact that the meal only had cheese is not a problem at all - there was probably sufficient protein in that meal on what the body truly needs. Where I see the problem is that it seemed like incomplete protein - there should have been nuts, soy or sesame of some type there to give you complete protein and a more balanced meal.

FYI I don't think they bill the pasta as vegetarian, rather just a pasta meal. The number of times I have ordered a veg meal, I can count on 1 hand the times I was served pasta as you described.