Blizzard Exchange

Hello! This question is more for curiosity’s sake.

Is there some policy against asking to exchange a blizzard if you just picked it up, and it tastes off from what it’s supposed to? Ordered an Oreo blizzard through drive-thru, tasted it and turned around to ask for an exchange. There was a weird, chemical aftertaste that isn’t usually there. The girl said “sorry, we can’t take it back” so I just left it at that, and have to take the hit for the $7. It just seems strange that being it wasn’t a matter of “I’m regretful I ordered this new flavor I’ve never tried” and that I took literally one spoonful, that they wouldn’t make me another.