I recently saw a snack container, where at the bottom - which you would see after eating the contents of the container - there was a label that read "contains no pig fat". This label / warning was not visible from the underside... only after you ate the food.
If you had a dietary restriction on eating pork or fat, it's already too late... if there were any in the food product.
This is some kind of ... ex post facto notification. I have heard people give 'warnings' like this after it is too late for the warning to affect behavior. The cause of the tardiness is either absentmindedness or other mistake.
Does a name, term, or phrase exist for some kind of reassurance, that is in the style of a warning, but is too late to ever warn you?
Note: I am not looking for an idiomatic-expression. The fact that this is a useless warning is important to me. I think this is a mu-style question!
I am hoping for a term that describes this issue, in context to the kind of problem (i.e. a warning). Neologisms are fine, if they do it right.