I take the opposite viewpoint of most people here.
Nothing in the game is necessarily permanent.
If your Dex is 13 and you gain the Dodge feat, do you suddenly lose that feat if you have temporary Dex loss due to poison?
Do you lose the Dodge feat with a permanent Dex drain due to a magical trap or a creature?
If the answer to either of these questions is yes, then what happens when your Dex is restored via a Restoration spell? Does the same thing happen as per the Headband of Intellect and skills argument? To me, that is silly for it to work one way in one case and a different way in a different case.
I view characters as a flow of abilities and items. The potion you had yesterday, you may no longer have today.
Ditto for pre-requisites. It doesn't mean that every time you lose a pre-requisite for some ability, feat, or PrC that you lose the rest of those abilities. It means that the talent you need to qualify no longer exists, but you have since learned those abilities, regardless of no longer having the talent to learn them again. IMO.