The other aspect to this, even if the crew are willing to give you one of their meals, is that the person bringing you your hot meal, is 99% of the time, not the person running the galley or who would have taken the original meal orders in the first place. So, it is probable that the person you are asking genuinely does not know what is left as they are not aware of the figures of what was loaded, what was ordered and if there are things lefts from each selection.