I guess you ask this question because you know that there are limiting amino acids in the vegetarian food. In your example that limiting amino acid would be lysine. However, I think that your question is theoretical and cannot be applied to real life as such. The reason is that there is an amino acid pool in the body where amino acids are stored at least for four hours, probably longer. If you eat lysine containing foods - e.g. beans, peas, milk products - at the same day, you get the limiting amino acids and in that way the proteins of your sandwiches are completed. If you don't, your meal would contain somewhat less usable protein.
