Look, the truth is I don't care what you put on your menu. (Well of course I do ... but i don't). If you want to serve elephant, serve elephant. (Not really). But for Dog's sake put a notation there. Let us know. An asterisk, a little "V" with a line drawn through it. How about just the words "Contains whey" in the description?? I felt ... taken advantage of. How disingenuous.
Now take a look at this picture of the menu at Gobo, another place I enjoy eating at: