Impossible to cancel the purchase of an item

I was just in a game where I mistakenly bought an item I already had a second time, never left the fountain, and yet I couldn't cancel the purchase. I then went on to sell two cookies (the ones you get from the rune page), and cancelling that sale worked.

So either I missed an element from one of the latest patches changing how reselling/cancelling the purchase of items works, or I encountered a bug.