Try keeping powdered milk on hands. I do that. I don’t like to drink it that way myself, but it is handy for such situations, and it keeps better than liquid milk. They sell it in resealable bags now, which makes it keep even better, because it can’t draw dampness. I realize my advice doesn’t do you much good for you right now, but it will make things better for you in the future. I have experienced the problem sometimes of having something cooking, and then realizing I am low on milk, or out, or it has spoiled. It is kind of a pain.