I mean, in real life with copyright stuff. Once you allow someone to use it. You can't just take it back afterwards.
You can't simply revoke someone's right to use an image after the fact, because you don't like them anymore.
The artwork was clearly specifically created for coco's team, it was commissioned by coco for this very thread. Therefore he has given him implicit permission to use this artwork for this thread.
Now as I highly doubt these two wrote up a contract, there is nothing that can stop coco from legally using this image.
Oral agreements are still agreements and once you give someone unrestricted permission without a termination clause, they can use the image freely.
To me this seems like a terrible decision from the administration team.