You decided to continue to place an order despite staff informing you that the options were limited. Therefore, you and your mother made a personal informed choice and you cannot complain about your limited options. How on earth do you even justify that? When you were told, you could have done what most people would have if they were not satisfied with what was available to them and leave.
Restaurants at times do run out of things, and they were on top of this by informing you straight away, you did not receive a poor service because they had ran out of some stock.
I find it hard to believe they would put another sauce on your sandwich considering how strict places are regarding allergies and dietary requirements. Nonetheless, they made you a sandwich that you felt was not up to standard - yet you still chose to eat it and not return it. You could have quite easily refused it, ordered something else as you're not vegetarian and have other options available.
Regardless of the fact you ate this sandwich which did not meet your standards, the staff offered to take the value off of your total as they acknowledged they were not able to give you everything you initially intended to eat. That was them providing you a great service by going on step further and offering you a discount.
Your frustration can be justified, sure, but you made an informed decision to stay there. But your comment to the staff was unwarranted and rude, it was not necessary you simply should have been gracious as you ate what they provided.
You've written a thread, people have told you you are unreasonable and yet instead of acknowledging others opinions you are adamant you're correct. So, what did you bother writing this thread for? Since then you've been arrogant and patronising, but I'm sure you've made many have a mid-week laugh as you just look ridiculous for being so dramatic over a non-issue.
Anyway, thanks for the laugh hun. I look forward to finding out who will play you in the movie.