JDiver

One problem is catering (often LSG SkyChefs, a division of Lufthansa Sky Group, or Gate Gourmet (Gate Group of Switzerland) sometimes gets it wrong - e.g. delivering salmon mains instead of chicken, etc. The FA can't serve what isn't available, so cobbing something together as described above is the answer. (sluggoaafa recently had this issue as he described it in another thread - he could not fulfill the wishes of those passengers who pre-ordered the chicken, or were allergic to fish, as the caterer didn't load the correct meals for the flight).

The other problem, of course, is AA does not fly BOM-IAH, so which flights did they not get their VGML that was operated by American? Was it NRT-DFW? Not complaining, but asking, the FAs can often get some other vegetarian dishes (salads, fruit) together.

As you were not flying, I am not sure you would get compensated. You can always try, but it's not any help for your parents. I'm sorry they had this problem.