What islam says about debt pardon?

I owe money to a non-muslim. But this person does not remember or does not want to remember how much I owe them after some years. And they say I don't owe them anything. I tried to discuss the issue so I would not pay a substantial larger amount, however this person is playing mind games, making me feel bad for wanting to pay and mixing emotions with the fact that I always said that I would return such money in each occasion I asked for it. Should I assume that this is a debt pardon? Is there such thing in Islam? I have two modest options: - Giving the money anonymously to them (even if it's more than the actually debt, since wasn't noted) - Assuming the debt is pardoned by them and going forward I am inclined to the first option, since is what I think it'll make my heart comfortable, and the Quran basically says to pay them and to fear Allah. But maybe the money would be more worth spending in zakat? Islamic references, if any, on the issue are appreciated.