From a food safety perspective, it depends on how the potatoes were cooled after being heated. If the potatoes were put right into the fridge, they will be fine. However, if the potatoes were left out at room temperature, but sealed tightly in the aluminum foil, you should discard the potatoes. When potatoes are sealed up tightly in foil at neither a hot nor cold temperature, this is similar to the canning process. Botulism can result if the potatoes were left lukewarm for a lengthy period of time.