I had a similar "save" by using our stored powdered milk... the wife was in the middle of making a German Chocolate Cake for me, and realized that she did not have the Evaporated Milk for the icing.

With a little online research, I was able to find out how to "make" the Evaporated Milk from powdered milk.
The cake turned out great!

Others might find this web page useful... Hillbilly Housewife ... lots of recipes/substitutions for powdered milk.