Yes but in our country (same with crwth) receipts often looks like that so I can attest that he is showing you the exact receipt that he did get from purchase. I don't think being grilled like this have some sort of chance to lie of what was being wanted by most of us here don't you think? Also it does prove something of their spent from the charity money, so I think that's a common sense it did prove something.
Traditionally in finance, management, scientific research, there are retention periods. In which you will have to store all records safely and rules for destruction of data.
I don't think we have such things with spontaneous charities. There are no Memorandum of understanding (MOU). I meant in spontaneous activities, such requirements only be raised after suspicious things which can be right accusation or just misunderstanding or mis-communication. In the end, operators will bear the most disadvantages.
So as I said, if you want something clear and professional, go to big charity foundations which are easily to find. If you participate in spontaneous charities & have clear ideas about what might happen, you should bring such requirements at beginning before you send your donation.
As I said, it is not my backing words for this charity. Just fact in life!