Hi, I am Keanus/Keani (yes, a cat who goes by many names). I am the owner of the character Kvar, and I was trying to upload a picture just now of my character.
https://inkbunny.net/s/799269
When I tried to upload it, I got a warning that it was a duplicate of a picture that apparently got deleted about two years ago. Saucy, the artist, prefers that their art not be posted, unless as it says on their page
https://inkbunny.net/Saucy
it was made for the poster. Is it possible for me to somehow undo this takedown? Should I get in contact with the artist, or otherwise prove that I am in fact the owner of the art?
https://inkbunny.net/s/798333
You can also see it on the artist's page here
Thanks for any help you can give, sorry if this is already answered, I have searched and cannot find anywhere that explains how I could go about it (as I assume it is unusual)

First of all, I would strongly recommend checking whether the artist is on the DNP list before trying to upload their work to the site.

As for your question - you should contact the artist, obtain special permission to upload the images in question to e621, and take it to NotMeNotYou, the head admin.
Sending proof to them via a DMail would probably be ideal. This kind of thing is not terribly common, but it happens (ex. post #2688339, see the description).

Either way, you should not attempt to reupload the image until the situation is resolved.
You might not have to upload anything at all - post #616740 can be undeleted relatively easily. But that's something to be discussed with NMNY.

keani said:
[..]
Should I get in contact with the artist, or otherwise prove that I am in fact the owner of the art?
[..]

Just to add to BitWolfy's reply, if you commission art from an artist they still own the art, a commission is paying them to make it for you but it's still theirs unless they say it's yours in writing.

With the artist owning the art you'd need to do as BitWolfy said, getting permission from the artist to post it to E6 and messaging NotMeNotYou with the proof. I'm pretty sure screenshots of DMs work fine for that.

bitwolfy said:
First of all, I would strongly recommend checking whether the artist is on the DNP list before trying to upload their work to the site.

As for your question - you should contact the artist, obtain special permission to upload the images in question to e621, and take it to NotMeNotYou, the head admin.
Sending proof to them via a DMail would probably be ideal. This kind of thing is not terribly common, but it happens (ex. post #2688339, see the description).

Either way, you should not attempt to reupload the image until the situation is resolved.
You might not have to upload anything at all - post #616740 can be undeleted relatively easily. But that's something to be discussed with NMNY.

You made the woopsie of mentioning re-uploading where the posting being un-deleted would be the course of action taken should it go through. Granted unless the post they wanted to upload is of superior quality