Chatting with a friend who's already graduated, has anyone encountered this situation?

When my friend and I were trading cards, I didn't realize it was his last one. I thought I'd let him initiate the trade, so he got it directly, and I wasn't in a hurry to receive it 😆 He might have been busy transferring cards that day and only told me in the afternoon that he got an error when he accepted. Then he tried again and got the same error. Turns out the old man didn't want him to graduate, but I ruined the old man's plan 🤣🤣🤣