I don't know. Maybe I'm just too easy to get along with. But it seems to me that a store should have the right to cut off the returns at some point. And three months seems like a fair length of time to wait.
If anything, I'd say the person who gave the gift is rude to have made you think it might be returnable.
But you got $20 out of it, so, always look on the bright side of life.